bugfix: midi thru from udp to usb triggers an assert()

    usbmidi supports 16 virtual cables (nCable in the code)
    any midi message received from udp sets this to 24 which is invalid.
    This replaces 24 with 0

Author: penfold42

src/udpmididevice.cpp

@@ -28,7 +28,7 @@
 #include <circle/net/netsubsystem.h>
 #include <circle/net/in.h>
 
-#define VIRTUALCABLE 24
+#define VIRTUALCABLE 0
 
 LOGMODULE("udpmididevice");
 
@@ -113,4 +113,4 @@ void CUDPMIDIDevice::Send(const u8 *pMessage, size_t nLength, unsigned nCable)
             LOGNOTE("Sent %zu bytes to UDP MIDI host (broadcast)", nLength);
         }
     }
-}
+}