Error uploading banner image for the group

Hi, I’m trying to upload a banner image for the group, i resized it to 240KB as well and tried uploading with various formats but i wasn’t able to… Here is the error i’m getting: Error uploading banner image: global name ‘_’ is not defined. I appreciate if you could help. Thanks in advance.

EDIT: I was able to eliminate the problem by taking down the resolution drastically. What is the limit for the resolution? (An error message with some info (max resolution etc.) might be more helpful for the future…