Bug report for Windows version 1.6.4

[Steve Sheridan]

I use the Windows version 1.6.4. The program consistently crashes 
whenever I have an empty superscript or subscript box, and try to click 
anywhere outside of the box without entering anything into the box first.

I haven't found this bug on the Bug Tracker, but I might have missed 
it--it seems like a big one. Let me know if you need more information to 
replicate the bug.

Steven Sheridan