Prevent compiler warning without panicking

[christiangnrd]

My attempt at resolving #1068.

The source of the panic seems to be an assertion that was added purely to remove a compiler warning, so I turned it into a warning because I don't think an empty version field should prevent updating to a latest PR.

TODO: If people decide this is an acceptable solution, I'll improve the warning message with potential causes.

One cause is when an installed channel has an empty version field due to not being able to get the version number from a non-codesigned executable on macOS #1068 (comment). It could also be that a particular PR was merged #1068 (comment).

[IanButterworth]

not being able to get the version number from a non-codesigned executable on macOS

Good call. Although I tried adding a pr channel, julia didn't load because of this.
I feel we should make that clearer to the user somehow.

[davidanthoff]

So if the underlying issue at the moment is that pr channels just don't work, then maybe we should (in the very short run) disable that feature on MacOS, and then try to properly fix #1000.

But I think we should not just start to ignore these empty versions at this place here, instead we should probably just abort installation of a PR channel if we can't launch the executable to extract the version in the first place.

[christiangnrd]

So if the underlying issue at the moment is that pr channels just don't work, then maybe we should (in the very short run) disable that feature on MacOS, and then try to properly fix #1000.

But I think we should not just start to ignore these empty versions at this place here, instead we should probably just abort installation of a PR channel if we can't launch the executable to extract the version in the first place.

While I agree #1086 is a much better solution. I think that this PR would be a better very-short-term solution than disabling the feature for mac users because it prevents a crash when trying to update, and still allows to download/update a PR branch. Users can then manually codesign the downloaded PR if they want.

[davidanthoff]

You convinced me :)