[winswitch] Failed to encode packet error using xpra-0.8.3

[Antoine Martin]

(snip)
> Somewhere in your initial packet is a "None" value, this shouldn't
> happen and the encoder is failing because of that.
> 
> (snip)
>>
>> Any suggestions?
>>
> If you can run with "-d all", you should see the full packet printed,
> and somewhere in it is going to be the value "None". If you can tell me
> where that is, I can fix it asap.
Just a wild guess from the depth of the stacktrace, the "None" value
might come from the "get_screen_sizes" call, so running:
xpra ... -d all | grep get_screen_sizes
Might gives us a clue.