Improve shutdown time of Controller Handler.

controllers/mattchbox_usb.py

@@ -68,7 +68,9 @@ class MattchBox(Controller):
         if port:
             # connect to serial port
             self.ser = serial.serial_for_url(port, do_not_open=True)
+            if self.ser:
                 self.ser.baudrate = 2400
+                self.ser.timeout = 0.1 # Speed up waiting for a byte.
                 try:
                     self.ser.open()
                     self.logger.log.info("Connected to serial port {}".format(port))
@@ -88,6 +90,7 @@ class MattchBox(Controller):
                 self.ser and self.ser.is_open and self.port
             ):  # If self.port is changing (via state_handler), we should stop.
                 try:
+                    if self.ser.in_waiting > 0:
                         line = int.from_bytes(
                             self.ser.read(1), "big"
                         )  # Endianness doesn't matter for 1 byte.