Steps to reproduce

1. Create a submodule in SourceTree with '.' in the path eg:

   [submodule "test.submodule"]
           path = test.submodule
           url = http://kahloun.foong@localhost:7990/scm/tst/stash.git
   

2. Right click on the submodule name in SourceTree and select 'delete'
3. An error will occur (refer to screenshot) and the .gitmodule file is corrupted:

           path = test.submodule
           url = http://kahloun.foong@localhost:7990/scm/tst/stash.git
   [submodule "tes"]
   submodule}.url=(null)
   submodule}.path=(null)
   

This happen to SourceTree for Windows 0.9.2.2 too