Halt on non-existent 'Save Directory' path

What steps will reproduce the problem?
1. Run Squash. Create a New Folder on Desktop and specify it as Save Directory 
for the output resized images. Continue using it. it works fine.
2. Next time you run Squash, the Save Directory from last run will be 
maintained. Now, if the folder was removed/renamed/moved, and you try to resize 
images, it will just halt. 

What is the expected output? What do you see instead?
An error message shows "non-exixtent Save Directory" or "specify a valid Save 
Directory"

What version of the product are you using? On what operating system?
Squash 0.3

Please provide any additional information below.
It's a great application, BTW. Thanks for it.

Original issue reported on code.google.com by amirhoss...@gmail.com on 30 Apr 2012 at 7:38

cristianocgv / squash

Halt on non-existent 'Save Directory' path #8