Repo tab unusable if an error message appears

If an error message appears when staging a file, the error message dialog won't go away. I need to either close the Repo tab, or close SourceTree. This is frustrating since I lose my commit message.

STEPS:
1) click Working Copy
2) have some files in Unstaged
3) click on a file in Unstaged and contrive an error message to appear.
4) observe error message dialog. E..g
>>>
fatal: Unable to create 'C:/dev/Space/Main/.git/index.lock': File exists.
If no other git process is currently running, this probably means a git process crashed in this repository earlier. Make sure no other git process is running and remove the file manually to continue.
Completed with errors, see above.
<<<
5) try clicking on the Close button
6) observe it doesn't do anything
7) observe all the repo action buttons are greyed out

EXPECTED
6) Close makes the error message go away

NOTE ON MAKING ERROR HAPPEN:
I get the "index.lock" error or other errors pretty easily in a couple of different circumstances.
1) a file that another process has locked
2) clicking on multiple files in the Unstaged area before waiting for them to finish

In fact, for case #2 it's arguably another bug. SourceTree is pretty unstable and if you click on a second file while it's still staging the first file, you get an error message.