Crash on double-clicking roster contact with subscription request

Versions

• OS: Linux
• GTK+ Version: 3.22.30
• PyGObject Version: 3.28.3
• python-nbxmpp Version: 0.6.7
• Gajim Version: 1.0.99

Traceback

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/gajim/dialogs.py", line 888, in on_authorize_button_clicked
    AddNewContactWindow(self.account, self.jid, self.user_nick)
  File "/usr/lib/python3/dist-packages/gajim/gtk/add_contact.py", line 147, in __init__
    if model[iter_][0] == transport:
UnboundLocalError: local variable 'transport' referenced before assignment

Steps to reproduce the problem

1. Receive a subscription request
2. Double-click the item that shows up in the roster for this new contact