Source Tree 2.6 crashes when opening repository in new tab

Summary

In Mac OS 10.12.6, when trying to open a second repository in a new tab, SourceTree crashes. This only happens when the first repository is in fullscreen mode.  When not in fullscreen mode, the second repository opens in a new window, instead of in a new tab. The ability to open new tabs instead of new windows was introduced in the latest Mac OS (How to use tabs in Mac OS Sierra ).

Steps to reproduce

1. Open a repository in SourceTree and make it full screen

1. On the top bar, go to File > Open recent and select another repository

1. SourceTree will crash

Note: when not in full screen mode, the new repositories will open in new windows as normal.