Crash when rolling the mouse wheel over preview

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Open Photivo
2. Go to File Manager
3. Point the mouse cursor over the image preview window and roll the mouse wheel

What is the expected output? What do you see instead?
I expect nothing to happen (it happens when I inadvertently rool the mouse 
wheel), but Photivo crashes.

What version of the product are you using? On what operating system?
Photivo 2013-07-01 64-bit, on Windows 7 Pro SP1 64 bit

Original issue reported on code.google.com by [email protected] on 6 Sep 2013 at 2:34