User-Agent:       Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.63 Safari/537.31
Build Identifier: 

Choose a project that is not podir/gettext. Go to version page and upload source document. Choose a pot file and upload. First upload will work ok but afterward an  error is shown on UI but no stacktrace in server log.

Reproducible: Always

Steps to Reproduce:
1. Choose a project that is not podir/gettext
2. Go to version page and upload source document (where msgctxt is null)
3. Choose a pot file and upload
Actual Results:  
First upload will work ok but afterward an error "Invalid POT file contents on file: xxx.pot" is shown on UI. No stacktrace in server log.

Expected Results:  
We may give a warning or stop users from uploading pot file to non-po project. At the very least, we should log exception in server log. In this case, the error is caused by treating the pot file as offline po and tried to use msgctxt as id. In this case the msgctext is null.