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

Fixes fix for Bugzilla #3408.
diff --git a/src/joystick/android/SDL_sysjoystick.c b/src/joystick/android/SDL_sysjoystick.c
index 89b8163..4225099 100644
--- a/src/joystick/android/SDL_sysjoystick.c
+++ b/src/joystick/android/SDL_sysjoystick.c
@@ -539,7 +539,9 @@
 SDL_SYS_JoystickClose(SDL_Joystick * joystick)
 {
     SDL_joylist_item *item = (SDL_joylist_item *) joystick->hwdata;
-    item->joystick = NULL;
+    if (item) {
+        item->joystick = NULL;
+    }
 }
 
 /* Function to perform any system-specific joystick related cleanup */