Attach Screenshot doesn't work when attaching from Rapid Board

Steps to reproduce

1. Install JIRA 6.3.7 and JIRA Agile 6.6
2. Create a board with some issues
3. Try attaching a screenshot to an issue through this board
   • Copy a screenshot to a clipboard
   • In Plan mode, click on the issue, then the ... at the top right of the screen, then Attach Screenshot
4. Paste the screenshot (Ctrl + V)

Expected Results

1. Screenshot is attached

Actual Results

1. Nothing is pasted with you click (Ctrl + V)
2. Will run into 500 error when you click Upload
3. Nothing will happen when you click Cancel
   • You will not return to the previous page

Notes

1. If you manually view the issue and click More > Attach Screenshot, issue will be pasted and everything works as normal
2. Tested with JIRA 6.3.7 and JIRA Agile 6.6
3. Tested with Mozilla and Chrome