Fix crashing when trying to connect a netplay session

src/drivers/libretro/libretro.c

@@ -532,6 +532,8 @@ void retro_set_input_state(retro_input_state_t cb)
 }
 
 void retro_set_controller_port_device(unsigned port, unsigned device)
+{
+   if (port < 2)  /* port #0 = player1/player3, port #1 = player2/player4 */
    {
        switch(device)
        {
@@ -543,7 +545,7 @@ void retro_set_controller_port_device(unsigned port, unsigned device)
              break;
        }
    }
-
+}
 
 void retro_set_environment(retro_environment_t cb)
 {