If a print is completed, it's now also updated in UI

CL-541

plugins/USBPrinting/USBPrinterOutputDevice.py

@@ -186,6 +186,8 @@ class USBPrinterOutputDevice(PrinterOutputDevice):
 
     def _sendNextGcodeLine(self):
         if self._gcode_position >= len(self._gcode):
+            self._printers[0].updateActivePrintJob(None)
+            self._is_printing = False
             return
         line = self._gcode[self._gcode_position]