SparkFunDMX fix for possible array bounds violation in DMX.write

Align with code in espdmx.cpp

wled00/src/dependencies/dmx/SparkFunDMX.cpp

@@ -34,8 +34,8 @@ static const int enablePin = -1;		// disable the enable pin because it is not ne
 static const int rxPin = -1;       // disable the receiving pin because it is not needed - softhack007: Pin=-1 means "use default" not "disable"
 static const int txPin = 2;        // transmit DMX data over this pin (default is pin 2)
 
-//DMX value array and size. Entry 0 will hold startbyte
-static uint8_t dmxData[dmxMaxChannel] = { 0 };
+//DMX value array and size. Entry 0 will hold startbyte, so we need 512+1 elements
+static uint8_t dmxData[dmxMaxChannel+1] = { 0 };
 static int chanSize = 0;
 #if !defined(DMX_SEND_ONLY)
 static int currentChannel = 0;