Right click on a commit with at least one child commit, select "rebase children of ... interactively" and then "Edit Message" of one of the child commits, then hit OK. Sourcetree crashes with 2 windows errors in a row:

1) Problem signature:
Problem Event Name: CLR20r3
Problem Signature 01: sourcetree.exe
Problem Signature 02: 1.6.11.0
Problem Signature 03: 5469eb24
Problem Signature 04: MultiSelectTreeView
Problem Signature 05: 1.0.0.0
Problem Signature 06: 5469eb0c
Problem Signature 07: be
Problem Signature 08: 85
Problem Signature 09: System.NullReferenceException

2) Problem signature:
Problem Event Name: APPCRASH
Application Name: SourceTree.exe
Application Version: 1.6.11.0
Application Timestamp: 5469eb24
Fault Module Name: KERNELBASE.dll
Fault Module Version: 6.1.7601.18409
Fault Module Timestamp: 5315a05a
Exception Code: c000041d
Exception Offset: 000000000000940d
OS Version: 6.1.7601.2.1.0.256.4
Locale ID: 1033
Additional Information 1: 8bac
Additional Information 2: 8bacfca9d396c3e2ec3c722825aa6254
Additional Information 3: 4a1d
Additional Information 4: 4a1d2e2706dc308df9a8fae9db4dd607