SourceTree fails to open a sub-repo. and crashes, whenever this same sub-repo. has an improper "branch" configuration.

Error returned:
System.ArgumentOutOfRangeException: startIndex cannot be larger than length of string.

I started working on my Git repo. straight with SourceTree 2.0, and since then I could not open one of my sub-repositories (main repo. and all sub-repo. retrieved from remote). I ended up using the CLI to interact with it.

The configuration file is at let us say @C:\Git_repo\.git\modules\mySubRepo\config.

Incorrect configuration:
[branch "origin/master"]
   remote = .
   merge = refs/heads/master

Correct configuration (solving the crash):
[branch "master"]
   remote = origin
   merge = refs/heads/master

I have no clue how/why this configuration was generated this way.

Attached is a modified extract from %localappdata%\SourceTree-settings\beta*.log.