Edje smart: Add NULL safety

This case actually happens with E. It's invalid but still happening,
and because Eo doesn't actually check the parent (or its type) fully,
an invalid, non-NULL object was returned.

See T2336 (this is not fixing the root cause!).

src/lib/edje/edje_smart.c

@@ -19,6 +19,7 @@ EAPI Evas_Object *
 edje_object_add(Evas *evas)
 {
    Evas_Object *e;
+   EINA_SAFETY_ON_NULL_RETURN_VAL(evas, NULL);
    e = eo_add(MY_CLASS, evas);
    return e;
 }