Throw an RAII lock around the conveyor to avoid a race condition

TextCanvas.py

@@ -105,6 +105,7 @@ class TextCanvas:
 		# So far simply does maintenance once per second
 		while self.__conveyor_enabled is True:
 			
+			with RAIILock(self.__lock):
 				self.__fps_samples.append(0)
 			
 			time.sleep(1)