1. Attempted to merge a branch into another as normal.
2. Received some conflicts to resolve
3. Right click a conflicted file and select "Resolve Conflict > External Merge Tool"
4. Currently have Beyond Compare 3 configured, It launches and you can complete the merge as normal
5. Close beyond compare and save the merge

Source Tree crashes. This is repeatable.

Not sure how to get any logs, just got a standard window app has crashed prompt which normally means its been uncaught. I attached visual studio debugger to it and got this exception

System.NullReferenceException was unhandled
Message: An unhandled exception of type 'System.NullReferenceException' occurred in SourceTree.Api.UI.Wpf.dll
Additional information: Object reference not set to an instance of an object.