mi: don't crash if we're trying to update the pointer for a keyboard.

If a device doesn't have a pointer, just return.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

mi/mipointer.c

@@ -367,6 +367,9 @@ miPointerUpdateSprite (DeviceIntPtr pDev)
 
     pPointer = MIPOINTER(pDev);
 
+    if (!pPointer)
+        return;
+
     pScreen = pPointer->pScreen;
     if (!pScreen)
 	return;