Don't use gps.time unless we're in debug mode

iot/main/gps.cpp

@@ -43,7 +43,11 @@ GPSLocation gps_fetch() {
 			// NOTE: It can take a rather long time to get a lock. Just wait patiently :-)
 			if(millis() - ms_last_update > 500) {
 				ticks++;
+				#ifdef SD_DEBUG_ENABLED
 				Serial.print(gps.time.isValid() ? '-' : '.');
+				#else
+				Serial.print('.');
+				#endif
 				if(ticks > 80) {
 					Serial.println();
 					ticks = 0;