wacom: don't fetch the dimensions if we're stopping live mode

There's just no point to that and if the tablet is currently in live mode, it
refuses the GET_WIDTH request anyway.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

tuhi/wacom.py

@@ -805,6 +805,7 @@ class WacomProtocolSlate(WacomProtocolSpark):
                                   self._on_sysevent_data_received)
 
     def live_mode(self, mode, uhid):
+        if mode:
             # Slate tablet has two models A5 and A4
             # Here, we read real tablet dimensions before
             # starting live mode