Added missing operator bool to USBSerial. Note. Its odd that I'd not spotted this was missing as I added it to HardwareSerial ages ago

STM32F1XX/cores/maple/usb_serial.h

@@ -49,6 +49,8 @@ public:
 	void begin(unsigned long, uint8_t);
     void end(void);
 
+	operator bool() { return true; } // Roger Clark. This is needed because in cardinfo.ino it does if (!Serial) . It seems to be a work around for the Leonardo that we needed to implement just to be compliant with the API
+
     virtual int available(void);// Changed to virtual
 
     uint32 read(void *buf, uint32 len);