Crash_when_disabling_syncing_in_the_webapp.mdwn

### Please describe the problem.
The watcher crashes.

I only need to restart the thread in the pop-up to get everything to work again, but I'm reporting just in case that this issue has any other implications.


### What steps will reproduce the problem?
I open the webapp and in the minutes before it starts syncing (syncing is enabled) I disable it (clicking in the 'syncing enabled' text).

This produces a crash every time.


### What version of git-annex are you using? On what operating system?
5.20140320 in Debian sid and testing


### Please provide any additional information below.
This is all I can see in the logs

[[!format sh """
Watcher crashed: PauseWatcher
[2014-03-26 08:54:57 CET] Watcher: warning Watcher crashed: PauseWatcher
"""]]