Fix minor resource leak in pg_dump

Michael Paquier, spotted using Coverity

src/bin/pg_dump/pg_dump.c

@@ -6596,7 +6596,7 @@ getTransforms(Archive *fout, int *numTransforms)
 	PGresult   *res;
 	int			ntups;
 	int			i;
-	PQExpBuffer query = createPQExpBuffer();
+	PQExpBuffer query;
 	TransformInfo   *transforminfo;
 	int			i_tableoid;
 	int			i_oid;
@@ -6612,6 +6612,8 @@ getTransforms(Archive *fout, int *numTransforms)
 		return NULL;
 	}
 
+	query = createPQExpBuffer();
+
 	/* Make sure we are in proper schema */
 	selectSourceSchema(fout, "pg_catalog");