fx: object: handle nullptr in object_ref and object_unref

fx/object.c

@@ -200,12 +200,19 @@ enum fx_status fx_object_get_data(
 
 struct _fx_object *fx_object_ref(struct _fx_object *p)
 {
-	p->obj_ref++;
+	if (p) {
+		p->obj_ref++;
+	}
+
 	return p;
 }
 
 void fx_object_unref(struct _fx_object *p)
 {
+	if (!p) {
+		return;
+	}
+
 	if (p->obj_ref > 1) {
 		p->obj_ref--;
 		return;