Created attachment 103085 [details]
Example crash report
(This is OS X specific, since LibreOffice is assumed to stay open; whereas it closes, unless quickstart is enabled, on Linux or Windows.)
If the last document/startcenter ("welcome screen") is closed (red button at top of window) while not focused on the app (i.e. menu bar does not say "LibreOffice"), then I can come back to LibreOffice by command-tab and then choosing something from the File menu or keyboard shortcut, or by clicking the dock icon (which opens startcenter).
I'm not sure these cases are reliable and what other conditions apply. One attempt, I can close last window but once I clicked the File menu, it crashed.
Following description + backtrace, it seems a dup of fdo#81387.
*** This bug has been marked as a duplicate of bug 81387 ***