Merge pull request #174 from per1234/fix-nano-33-ble-conditional

Make preprocessor conditional false when identifier undefined

Author: ladyada

DHT.h

@@ -47,7 +47,7 @@
 #define DHT21 21  /**< DHT TYPE 21 */
 #define AM2301 21 /**< AM2301 */
 
-#if (TARGET_NAME == ARDUINO_NANO33BLE)
+#if defined(TARGET_NAME) && (TARGET_NAME == ARDUINO_NANO33BLE)
 #ifndef microsecondsToClockCycles
 /*!
  * As of 7 Sep 2020 the Arduino Nano 33 BLE boards do not have