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

TextCanvas.py

@@ -105,7 +105,8 @@ class TextCanvas:
 		# So far simply does maintenance once per second
 		while self.__conveyor_enabled is True:
 			
-			self.__fps_samples.append(0)
+			with RAIILock(self.__lock):
+				self.__fps_samples.append(0)
 			
 			time.sleep(1)