I am currently using Source Tree. I am using Mac 10.11.6. I have BitBucket setup on SourceTree. It unexpectedly crashed last time when I used it. But now I can't launch this application anymore.
When I reopen SourceTree I get the error message "The last time you opened Sourcetree, it unexpectedly quit while reopening windows. Do you want to try to reopen its windows again?". Please see screenshot.

I tried clicking on both 'Don't Reopen' and 'Reopen' each option has the same outcome. The application just crashes as soon as it opens. I even tried to force quit and restart my Mac.