1. have an merge conflict
2. launch external merge tool (I use KDiff3)
3. resolve the conflict and close merge tool after saving the result
4. app crashes with NullReferenceException

Problem signature:
Problem Event Name: CLR20r3
Problem Signature 01: SourceTree.exe
Problem Signature 02: 1.8.2.2
Problem Signature 03: 56ccf1c1
Problem Signature 04: SourceTree.Api.UI.Wpf
Problem Signature 05: 1.8.2.2
Problem Signature 06: 56ccf1a1
Problem Signature 07: b4c
Problem Signature 08: 14
Problem Signature 09: System.NullReferenceException
OS Version: 6.1.7601.2.1.0.256.4
Locale ID: 1049
Additional Information 1: 71d5
Additional Information 2: 71d592cd9f7fe7b3113abce64fc3b90d
Additional Information 3: 2e4a
Additional Information 4: 2e4a57d24c4df3dddc80911828900078