Freeze-break: gnome-shell: network menu empty if wimax present

[Owen Taylor <otaylor redhat com>]

Currently we don't handle some less common types of networks in the
shell network menu (wimax, in particular). If one of these is present
the shell network menu currently throws an exception and comes up
empty.

Patch in:

 https://bugzilla.gnome.org/show_bug.cgi?id=646355

I believe is correct and fixes an artificially induced similar problem,
though I don't have wimax here to test.

- Owen