Cannot resize diff panel for uncommited changes

When viewing uncommited changes in both the 'File Status' tab and 'Log / History', and also having the 'Bookmarks' panel hidden, I am unable to resize the diff panel. There have been several Jiras about this in the past and it seems to have come back.

In order for me to resize the panel, I need to show the 'Bookmarks' panel. Interestingly enough, after hiding the 'Bookmarks' panel, I can continue to resize the diff panel. If all I do is show and then immediately hide the 'Bookmarks' panel, I cannot resize.

If I restart SourceTree, the problem is reset and I am unable to resize again.