Fix instance snackbar

[micahmo]

Pull Request Description

This PR fixes a strange issue where the snackbar indicating an error navigating to an instance would not appear unless the user interacted with the UI in some other way. I believe this is related to the fact that we're using addPostFrameCallback, but there's no other building operation happening. (Most if not all other snackbars are usually related to something that changes/builds at the same time). There may be a better way to fix this, and I'm open to ideas, but for now I just added a condition for whether to use the post-frame or not.

Issue Being Fixed

Issue Number: N/A

Screenshots / Recordings

Before

qemu-system-x86_64_yu2BDIbWoV.mp4

After

qemu-system-x86_64_h9IYsXv8uY.mp4

Checklist

• Did you update CHANGELOG.md?
• Did you use localized strings where applicable?
• Did you add semanticLabels where applicable for accessibility?

[micahmo]

Note that this might not be an issue now with #1218, but it might not hurt to have this option in the snackbar anyway.

[hjiangsu]

I think we can leave this out if its no longer needed! If we end up needing it in the future, we'll merge it in - just helps with keeping the codebase a bit cleaner 😅

[micahmo]

Sounds good, I'll close this PR but keep my branch just in case.