Git cleanup fails when submodules is enabled

When doing clean with submodules enabled I'm getting an empty error message box

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TortoiseGit
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OK   
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TortoiseGit 1.8.15.0 (C:\Program Files\TortoiseGit\bin) 
git version 1.9.5.msysgit.1 (C:\Program Files (x86)\Git\bin; C:\Program Files (x86)\Git\; C:\Program Files (x86)\Git\etc\gitconfig)

1.8.14 worked fine with the same repository and everything.

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