Profile: Upload image doesn't work in case of changed file extension

If you take file with changed extension from wrong to right (ex. doc. in jpeg) upload is failed.

Steps:

1. Go to http://qa.jtalks.org/jcommune/ and log in.
2. Open your profile.
3. Take any .doc on your computer and change extension on .jpeg.
4. Try to upload it with "upload" button.

Actual result: Error that says about wrong extension.
Expected result: The file will be upload because it have legal extension.