Some of the most usual causes for null pointer exceptions on Confluence are described on this below article:
However, just like Nic stated, you'll need to analyse the application logs in order to identify what is in fact causing the issue. In case you need further assistance with this, I suggest you raise a support ticket at https://support.atlassian.com/
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG