Update BLERemoteCharacteristic.cpp (#2800)

Prevents the error that is generated on free on row 186
When calling the function readValue() sometimes it gave an error on this free.

libraries/BLE/src/BLERemoteCharacteristic.cpp

@@ -39,6 +39,7 @@ BLERemoteCharacteristic::BLERemoteCharacteristic(
 	m_charProp       = charProp;
 	m_pRemoteService = pRemoteService;
 	m_notifyCallback = nullptr;
+	m_rawData = nullptr;
 
 	retrieveDescriptors(); // Get the descriptors for this characteristic
 	log_v("<< BLERemoteCharacteristic");