fix nullpointer in previous swipetorefresh fix
fix signatures produced by yubikey

The timestamp was only set on a second run. This led to a race
condition whether the signature could be completed within the
same timestamp.

Fixes #834
fix signing in OK with yubikeys
Merge remote-tracking branch 'origin/master'

Conflicts:
	OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/EncryptActivity.java