transports: smart: fix memory leak on OOM path

src/transports/smart_protocol.c

@@ -108,6 +108,7 @@ static int append_symref(const char **out, git_vector *symrefs, const char *ptr)
 		if (giterr_last()->klass != GITERR_NOMEMORY)
 			goto on_invalid;
 
+		git__free(mapping);
 		return error;
 	}
 
@@ -120,6 +121,7 @@ static int append_symref(const char **out, git_vector *symrefs, const char *ptr)
 on_invalid:
 	giterr_set(GITERR_NET, "remote sent invalid symref");
 	git_refspec__free(mapping);
+	git__free(mapping);
 	return -1;
 }