Do not allow to use DELETE key when not connected
Gajim allows to use DELETE key on (always offline) roster contacts when account is not connected.
This has no effect on roster (server-side), contact is restored after deletion.
Steps to reproduce
Use an offline machine. Start Gajim. View > Show Offline Contacts Select a contact. Press DELETE.
OS version: Salix OS 14.1 (Slackware 14.1 based) GTK version: 2.24.20 PyGTK version: 2.24.0