Issue Summary

Comment may disappear after pasting or uploading an image in the Issue Detail View on an agile board.

This is reproducible on Data Center: (yes) 

Steps to Reproduce

1. Click a ticket from Kanban board
2. Click 'Add Comment' 
3. Input some words (for example: this is a test)
4. Paste a image into it
5. Click some places in the ticket (for example: scroll bar of the ticket, try to add smiley, click + icon for text formatting)

Expected Results

Words and image in comment box should remain

Actual Results

Words and image disappeared

Workaround

Not using board view to add comment.
This problem won't happen when open it directly (https://aa.bb.cc/browse/XX-xx)