Stretch regions in Nine-patch Generator are not accessible if source image was resized to smaller

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Open some image and set bounds of stretch regions and/or content padding. 
Foe example 100*100px image, and bottom right point is at 90,90px.
2. Resize original image so it is smaller than right/bottom bound of region. 
ex. 50*50px
3. Open this image in Nine-patch Generator.
4. Try to move bottom/right egde of region. You can't beacuse it is out of 
viewport.

What is the expected output? What do you see instead?
Maybe some "reset" button.


Please provide any additional information below.
Settings are stored in cookies or somewhere else so you can't just reload page 
to make it work.

Original issue reported on code.google.com by CAJ...@gmail.com on 8 Nov 2013 at 9:39