Message editor breaks when tabcompleting names

[michaelkaye]

Steps to reproduce:

• Start with a normal text entry area "Send a message (unencrypted)".
• type "@to" and tab-complete to a name.
• Display now shows " :" - the pill containing the name has dissappeared.
• Press backspace twice, removing the ":" and " "
• Text entry area is now entirely empty (no "send a mesage"), loses caret and is now un-clickable to add new text.
• Clicking "M" button causes the box to recover by showing/unshowing the text formatted as markdown.
• At this point the caret is now available and text entry area can be deleted to get back to the "send a message prompt".

The issue is recoverable from, but is repeatable across channels and across tab-completed names, whether or not the tab completion is in the middle of the message or not (though the missing information in the middle of the message.

[jcgruenhage]

Also, while you can't see the pill, it is there. It appears upon sending.

[lampholder]

Anecdotally I feel like I'm seeing a lot of composer bugs suddenly :S

[lampholder]

This is only on /develop, not /app, so I'd hope we could track down the cause.