Android: Fixed crash if closing removed joystick (thanks, Sylvain!).

Fixes fix for Bugzilla #3408.

src/joystick/android/SDL_sysjoystick.c

@@ -539,8 +539,10 @@ void
 SDL_SYS_JoystickClose(SDL_Joystick * joystick)
 {
     SDL_joylist_item *item = (SDL_joylist_item *) joystick->hwdata;
+    if (item) {
         item->joystick = NULL;
     }
+}
 
 /* Function to perform any system-specific joystick related cleanup */
 void