fix pointer c is dereferenced after checking null

src/tests/get_item.c

@@ -555,7 +555,10 @@ int main(int argc, char *argv[])
 	printf("All get_item tests passed\n");
 	fret = EXIT_SUCCESS;
 out:
+	if (c) {
 		c->destroy(c);
 		lxc_container_put(c);
+	}
+
 	exit(fret);
 }