pdo_pgsql: cleanup

set S->result to NULL after having freed it (not crucial now, as it is immediately recycled)

Author: outtersg

ext/pdo_pgsql/pgsql_statement.c

@@ -198,6 +198,7 @@ static int pgsql_stmt_execute(pdo_stmt_t *stmt)
 					/* it worked */
 					S->is_prepared = 1;
 					PQclear(S->result);
+					S->result = NULL;
 					break;
 				default: {
 					char *sqlstate = pdo_pgsql_sqlstate(S->result);