Merge pull request #848 from sonninnos/led-interface

Crash fix for LED interface

libretro.cpp

@@ -4913,7 +4913,7 @@ void retro_set_environment(retro_environment_t cb)
 	   filestream_vfs_init(&vfs_iface_info);
 
    environ_cb(RETRO_ENVIRONMENT_GET_LED_INTERFACE, &led_interface);
-   if (led_interface.set_led_state)
+   if (led_interface.set_led_state && !led_state_cb)
       led_state_cb = led_interface.set_led_state;
 
    input_set_env(cb);