Update ngit submodule
Fix exception when recomputing diff margin rectangle boundaries
Fix NullReferenceException when opening a non-existent repository
Handle non-critical exceptions
Fix merge error (broken build)
Merge branch 'ngit-47afeb3' of https://github.com/sharwell/Git-Source-Control-Provider
Merge branch 'exceptions' of https://github.com/sharwell/Git-Source-Control-Provider