Fix panic condition on docker pull failure

[wagoodman]

When pulling a docker image and there is an issue, there is a panic when attempting to close the source:

❯ go run ./cmd/syft python:slim -o json
  ⠼ Pulling image
 panic: value method github.com/anchore/syft/syft/source.StereoscopeImageSource.Close called using nil *StereoscopeImageSource pointer
 
 goroutine 9 [running]:
 github.com/anchore/syft/syft/source.(*StereoscopeImageSource).Close(0xc00011c3e0?)
         <autogenerated>:1 +0x86
 github.com/anchore/syft/cmd/syft/cli/packages.execWorker.func1()
         /Users/wagoodman/code/syft/cmd/syft/cli/packages/packages.go:109 +0x92a
created by github.com/anchore/syft/cmd/syft/cli/packages.execWorker
        /Users/wagoodman/code/syft/cmd/syft/cli/packages/packages.go:57 +0xf7
 exit status 2

When fixing the panic, it was noticed that the UI was hung (but no more panicing!). There seems to be an underlying issue to fix in last-event handling in the syft event loop and error conditions in stereoscope, both of which have been deferred. In the meantime there was an additional change to not wait for the UI to teardown in kill situations, resulting in the following output:

❯ go run ./cmd/syft python:slims -o json
 ⠦ Pulling image                   
2023/07/27 11:18:59 error during command execution: 1 error occurred:
        * failed to construct source from user input "python:slims": unable to load image: unable to use DockerDaemon source: pull failed: Error response from daemon: manifest for python:slims not found: manifest unknown: manifest unknown

exit status 1

[github-actions]

Benchmark Test Results

Benchmark results from the latest changes vs base branch

goos: linux%0Agoarch: amd64%0Apkg: github.com/anchore/syft/test/integration%0Acpu: Intel(R) Xeon(R) Platinum 8272CL CPU @ 2.60GHz%0A                                                              │ ./.tmp/benchmark-4ee70f7.txt │%0A                                                              │            sec/op            │%0AImagePackageCatalogers/alpmdb-cataloger-2                                       12.31m ±  2%25%0AImagePackageCatalogers/apkdb-cataloger-2                                        740.7µ ±  5%25%0AImagePackageCatalogers/binary-cataloger-2                                       212.3µ ±  2%25%0AImagePackageCatalogers/dpkgdb-cataloger-2                                       632.2µ ±  5%25%0AImagePackageCatalogers/dotnet-portable-executable-cataloger-2                   22.25µ ±  1%25%0AImagePackageCatalogers/go-module-binary-cataloger-2                             97.05µ ± 16%25%0AImagePackageCatalogers/java-cataloger-2                                         13.97m ±  2%25%0AImagePackageCatalogers/graalvm-native-image-cataloger-2                         98.46µ ±  2%25%0AImagePackageCatalogers/javascript-package-cataloger-2                           403.2µ ±  1%25%0AImagePackageCatalogers/nix-store-cataloger-2                                    290.3µ ±  1%25%0AImagePackageCatalogers/php-composer-installed-cataloger-2                       833.6µ ±  0%25%0AImagePackageCatalogers/portage-cataloger-2                                      503.9µ ±  1%25%0AImagePackageCatalogers/python-package-cataloger-2                               3.506m ±  3%25%0AImagePackageCatalogers/r-package-cataloger-2                                    218.4µ ±  1%25%0AImagePackageCatalogers/rpm-db-cataloger-2                                       577.4µ ±  1%25%0AImagePackageCatalogers/ruby-gemspec-cataloger-2                                 952.0µ ±  1%25%0AImagePackageCatalogers/sbom-cataloger-2                                         121.9µ ±  2%25%0Ageomean                                                                         505.4µ%0A%0A                                                              │ ./.tmp/benchmark-4ee70f7.txt │%0A                                                              │             B/op             │%0AImagePackageCatalogers/alpmdb-cataloger-2                                       5.119Mi ± 0%25%0AImagePackageCatalogers/apkdb-cataloger-2                                        204.8Ki ± 0%25%0AImagePackageCatalogers/binary-cataloger-2                                       30.19Ki ± 0%25%0AImagePackageCatalogers/dpkgdb-cataloger-2                                       168.8Ki ± 0%25%0AImagePackageCatalogers/dotnet-portable-executable-cataloger-2                   3.696Ki ± 0%25%0AImagePackageCatalogers/go-module-binary-cataloger-2                             9.906Ki ± 0%25%0AImagePackageCatalogers/java-cataloger-2                                         2.823Mi ± 0%25%0AImagePackageCatalogers/graalvm-native-image-cataloger-2                         8.594Ki ± 0%25%0AImagePackageCatalogers/javascript-package-cataloger-2                           94.19Ki ± 0%25%0AImagePackageCatalogers/nix-store-cataloger-2                                    49.14Ki ± 0%25%0AImagePackageCatalogers/php-composer-installed-cataloger-2                       186.6Ki ± 0%25%0AImagePackageCatalogers/portage-cataloger-2                                      119.9Ki ± 0%25%0AImagePackageCatalogers/python-package-cataloger-2                               1.004Mi ± 0%25%0AImagePackageCatalogers/r-package-cataloger-2                                    53.29Ki ± 0%25%0AImagePackageCatalogers/rpm-db-cataloger-2                                       180.9Ki ± 0%25%0AImagePackageCatalogers/ruby-gemspec-cataloger-2                                 144.0Ki ± 0%25%0AImagePackageCatalogers/sbom-cataloger-2                                         14.20Ki ± 0%25%0Ageomean                                                                         100.3Ki%0A%0A                                                              │ ./.tmp/benchmark-4ee70f7.txt │%0A                                                              │          allocs/op           │%0AImagePackageCatalogers/alpmdb-cataloger-2                                        87.74k ± 0%25%0AImagePackageCatalogers/apkdb-cataloger-2                                         4.182k ± 0%25%0AImagePackageCatalogers/binary-cataloger-2                                         830.0 ± 0%25%0AImagePackageCatalogers/dpkgdb-cataloger-2                                        3.002k ± 0%25%0AImagePackageCatalogers/dotnet-portable-executable-cataloger-2                     132.0 ± 0%25%0AImagePackageCatalogers/go-module-binary-cataloger-2                               281.0 ± 0%25%0AImagePackageCatalogers/java-cataloger-2                                          39.88k ± 0%25%0AImagePackageCatalogers/graalvm-native-image-cataloger-2                           228.0 ± 0%25%0AImagePackageCatalogers/javascript-package-cataloger-2                            1.342k ± 0%25%0AImagePackageCatalogers/nix-store-cataloger-2                                      895.0 ± 0%25%0AImagePackageCatalogers/php-composer-installed-cataloger-2                        4.079k ± 0%25%0AImagePackageCatalogers/portage-cataloger-2                                       2.268k ± 0%25%0AImagePackageCatalogers/python-package-cataloger-2                                16.44k ± 0%25%0AImagePackageCatalogers/r-package-cataloger-2                                      929.0 ± 0%25%0AImagePackageCatalogers/rpm-db-cataloger-2                                        3.989k ± 0%25%0AImagePackageCatalogers/ruby-gemspec-cataloger-2                                  2.447k ± 0%25%0AImagePackageCatalogers/sbom-cataloger-2                                           394.0 ± 0%25%0Ageomean                                                                          2.051k