The way to reproduce the crash is simple:
Create a new Project using Third Person CPP base project
launch editor (after compiling sources of course)
Head to Mannequin → Animations → ThirdPerson_AnimBP
Editor will crash with following error:
[2017.01.12-17.45.50:283][839]LogMaterial: Missing cached shader map for material M_SkyBox, compiling.
[2017.01.12-17.45.52:628][839]LogContentBrowser: Native class hierarchy updated for ‘BlueprintGraph’ in 0.0038 seconds. Added 111 classes and 0 folders.
[2017.01.12-17.45.53:481][839]LogLinux:Error: appError called: Assertion failed: Assertion failed: IsValid() [File:Runtime/Core/Public/Templates/SharedPointer.h] [Line: 783]