Does the program become unusable?  I've tried that here, and, indeed, the "waiting" animation begins and runs forever.  However, if I return to the Project tree, open a file, and return to the outline tab, the outline pops right up.  Are you seeing something different?  Obviously, what I described is less than ideal, but I want to confirm the program continues working for you.

1. Open  an existing project.
2. Do not select any of the files.
3. Select file outline, file tab.
4. No files appear in the files list (as expected).
5. Click the circular-arrows 'update' icon.

Program seems to hang.

Is an error trap needed for this maybe?
I hope this report is helpful.
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John