Follow up to 82b4a53d29b6e043001e37cb448f077a19067a33
On mobile, we just need to add `min-width: 0` to
`chat-live-pane` so it will not overflow the grid
defined in `main-chat-outlet.chat-view`.
The overflow could be triggered by:
1. Replying on mobile to a really long chat message
2. Uploading > 2 files
Both of these situations are fixed.
c767a38086