Clicking on a compose-triggering location cancels current compose

[neiljp]

While this could be considered resolved if we had a drafts feature where messages were saved in these situations, this could still be as confusing as it feels now:

• Start replying to a message (eg. stream, PM), and type some text
• Click on any message in the message list, or a user name in the right (which also narrows!)
• ...and the message is lost

While clicking on a user name might be relatively expected to cause this behavior, if you click on a message in the same narrow, it has the same behavior. This wouldn't be to a different recipient, so this is a significant issue.

Strangely (?) this currently doesn't occur when clicking on the top-left narrow buttons, where the compose window is unchanged but the narrow view changes!

Various options for solving it could be:

• requiring GO_BACK to exit from composing (not responding to clicks)
• retaining message content, potentially changing recipients if moving around (dangerous?)
• not changing narrow or resetting compose until the message is sent or cancelled (GO_BACK?)