fix(vue-app): don't attach catch handler to already loaded component (fixes #5751)

[rchl]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

Components are not necessarily lazy-loaded. If user overrides webpack
build options with splitChunks:{layouts: false, pages: false}, for
example, pages will be loaded already on loading app.

I was thinking of handling this in the getPrefetchComponents function already, to not return components that are already loaded, but I don't see a way to find that out until we call Component() and that would trigger prefetching in case of lazy-loaded components.

Resolves: #5751

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-io]

Codecov Report

Merging #5752 into dev will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##             dev   #5752   +/-   ##
=====================================
  Coverage   95.6%   95.6%           
=====================================
  Files         82      82           
  Lines       2662    2662           
  Branches     683     683           
=====================================
  Hits        2545    2545           
  Misses        98      98           
  Partials      19      19

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