tools/utils: free memory on error

Closes #2262.

Signed-off-by: C0deAi <techsupport@mycode.ai>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/tools/tool_utils.c

@@ -794,8 +794,11 @@ int lxc_config_define_add(struct lxc_list *defines, char *arg)
 		return -1;
 
 	dent->elem = parse_line(arg);
-	if (!dent->elem)
+	if (!dent->elem) {
+		free(dent);
 		return -1;
+	}
+
 	lxc_list_add_tail(defines, dent);
 	return 0;
 }