Attempting to convert a non-existing file, results in misleading "No codec could be found" error message

[de-code]

When attempting to convert a non-existing document, e.g. running the following command:

./encoda convert this-file-does-not-exist.docx output.pdf

# or:
node dist/cli.js convert this-file-does-not-exist.docx output.pdf

It is showing:

⚠ WARN  encoda No codec could be found for source "this-file-does-not-exist.docx". Falling back to plain text codec.
🚨 ERROR encoda dom.setAttribute is not a function

It should instead show a message that the file doesn't exist.

That became an issue due to using ~ as a placeholder for the home directory (that isn't expanded by the above command, but is by using stencila, see #803 (comment)).