aioble/examples/temp_client.py: check connection before reading temp

Only read from the temp characteristic if the connection is still
active. Improves the example by avoiding a TypeError exception when the
sensor disconnects.

Author: rknegjens

micropython/bluetooth/aioble/examples/temp_client.py

@@ -54,7 +54,7 @@ async def main():
             print("Timeout discovering services/characteristics")
             return
 
-        while True:
+        while connection.is_connected():
             temp_deg_c = _decode_temperature(await temp_characteristic.read())
             print("Temperature: {:.2f}".format(temp_deg_c))
             await asyncio.sleep_ms(1000)