fix: Returns a warning instead of panicking if an AppImage is not mounted, closes #7736

[Benji377]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• New Binding issue #___
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #___
• No

Checklist

• When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary

Other information

When uploading an AppImage to the AppImage repository, Tauri checks if the AppImage is valid by trying to mount it and check a specific mount point. Unfortunately, many AppImages that are perfectly functional don't pass this test, and therefore the automatic AppImage Workflow fails.
To fix this issue, I simply replaced the panic with a warning. This would still give feedback, but at least let the AppImage finish running. I encountered this issue here and mayn other users have as well in the issue #7736

Basically, I am reverting some changes of the commit: 6fbd6db

Note: I used the log crate to display a warning, but if that's not ok with you, you are more than welcome to change that.

[probonopd]

When uploading an AppImage to the AppImage repository, Tauri checks if the AppImage is valid by trying to mount it and check a specific mount point.

...close ;-) This is what actually happens:

When submitting an AppImage to https://appimage.github.io/, then the automated test in that repository checks if the AppImage is valid by trying to run it with Firejail.

And since Tauri makes some assumptions about AppImages that do not hold true (and are not part of the spec), Firejail currently fails to run AppImages made with Tauri, preventing Tauri-based AppImages from passing the automated test.

So it would be best to entirely reverse-apply 6fbd6db since its assumptions are flawed to begin with.

The base branch was changed.