examples/mac: disable the cursor

We cannot write access the frame buffer, and we do not have a sensible
cursor anyway, so better disable the cursor (which would have to be drawn
for clients that do not support CursorShapeUpdates).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

examples/mac.c

@@ -464,6 +464,9 @@ ScreenInit(int argc, char**argv)
   rfbScreen->frameBuffer =
     (char *)CGDisplayBaseAddress(kCGDirectMainDisplay);
 
+  /* we cannot write to the frame buffer */
+  rfbScreen->cursor = NULL;
+
   rfbScreen->ptrAddEvent = PtrAddEvent;
   rfbScreen->kbdAddEvent = KbdAddEvent;