hang when trying to connect to the same callsign

[nivex]

Steps to reproduce:

• Establish connection (in my case, SWITCH, the BPQ internal endpoint)
• Switch to another connection tab
• Attempt to connect to the same callsign from the previous tab

Expected result:
A dialog of some sort telling me I can't do that.

Actual result:
UI goes away and a long traceback is printed. Relevant part:

  File "/home/kjotte/paracon_1.3.0.pyz/paracon.py", line 475, in _save_and_connect                                                                             
    self._make_connection(info)                                                                                                                                
    ~~~~~~~~~~~~~~~~~~~~~^^^^^^                                                                                                                                
  File "/home/kjotte/paracon_1.3.0.pyz/paracon.py", line 511, in _make_connection                                                                              
    conn = app.server.open_connection(                                                                                                                         
        port, info.connect_as, info.connect_to, vias)                          
  File "/home/kjotte/paracon_1.3.0.pyz/pserver.py", line 189, in open_connection                                                                               
    conn = self._engine.open_connection(port, call_from, call_to, via)                                                                                         
  File "/home/kjotte/paracon_1.3.0.pyz/pe/app.py", line 205, in open_connection                                                                                
    return self._connections.open(port, call_from, call_to, via)                                                                                               
           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^                                                                                               
  File "/home/kjotte/paracon_1.3.0.pyz/pe/connect.py", line 305, in open                                                                                       
    self._connection_map.add(conn)                                                                                                                             
    ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^                                                                                                                             
  File "/home/kjotte/paracon_1.3.0.pyz/pe/connect.py", line 245, in add                                                                                        
    raise ValueError('Connection already exists')                                                                                                              
ValueError: Connection already exists  

At this point the program is still running but it is hung. Only way out is Ctrl-C.