[Bug] select a document containing a PDF after clicking on the thumbnail of another document ends in a crash

[kaamui]

Describe the bug

select a document containing a PDF after clicking on the thumbnail of another document ends in a crash

To Reproduce

1. Go to Documents Mode
2. Click on a document A with no PDF
3. Click on thumbnail 1 to select it
4. Click on document B with a PDF

Expected behavior

A clear and concise description of what you expected to happen.

No crash

Actual behavior

A clear and concise description of what actually happened
A crash occurs (mLastSelectedThumbnail in UBDocumentThumbnailsView::resizeEvent)

Screenshots

If applicable, add screenshots to help explain your problem.

Additional resources

PDF, images, sounds... anything useful to reproduce the bug

Context

• reproducibility : systematic not systematic
• OpenBoard version :
  • bug happens with : dev
• OS :
  • bug happens with : Linux

[letsfindaway]

Can reproduce this! The additional commit I added to my PR 1241 however fixes this. I could no longer observe this issue after invalidating mLastSelectedThumbnail when switching documents.

[letsfindaway]

I'm still investigating whether I can provoke such a situation by other means, e.g. by deleting the last selected page.

And whether I find some kind of a smart pointer which gets automatically invalidated when the thumbnail is deleted, similar to QPointer but for non-QObjects.

[letsfindaway]

Fixed by OpenBoard-org#1241