If NetworkManager decides that a wireless connection has timed out
before "supplicant connection state" has occued, our idea of the state
is `undef`, so it cannot be used in a string comparison. Hence, let's
initialize the state to the empty string instead of `undef`.

Will-fix: #7689

It's been removed with #9597.

Fix-committed: #9890

Fix-committed: #9877

... so that we won't be nagged when testing Tails 1.5.1 (in
particular, that would break large parts of the automated test
suite). Apparently this was forgotten during the 1.5 release. Oops!

Fix-committed: #10112

Will-Fix: #10112