chatview: missing images are badly handled
How to reproduce:
- User A sends an image to user B
- User B receives the image and the chatview displays it successfully
- For some reason the image is deleted from user B's filesystem
- Whenever User B tries to display the conversation, the chatview now displays a white hole and the js logs report various resource access errors
What should happen: Instead of trying to display the broken/missing image we should display the usual file transfer canvas. We used to have some code for doing that but it is now broken and should be repared.