Save expanded URL between keypresses.

[Zegnat]

This one drives me crazy, but will be more than 3 lines of code and 10 minutes of testing so filing it as an issue for now. To fix this right would probably require saving the expanded version in the message object and keep it around as long as possible.

1. Hover over a shortened URL,
2. wait for it to be expanded,
3. press command to change the status bar text and see the extended URL disappear.