fix leak on failed conversion. new test case

Author: devnexen

ext/snmp/snmp.c

@@ -678,7 +678,8 @@ static bool php_snmp_parse_oid(
 		ZEND_HASH_FOREACH_VAL(oid_ht, tmp_oid) {
 			zend_string *tmp = zval_try_get_string(tmp_oid);
 			if (!tmp) {
-				continue;
+				efree(objid_query->vars);
+				return false;
 			}
 			objid_query->vars[objid_query->count].oid = ZSTR_VAL(tmp);
 			zend_string_release(tmp);

ext/snmp/tests/gh16959.phpt

@@ -17,6 +17,11 @@ var_dump($bad_object_ids);
 var_dump(snmpget($hostname, "", $bad_object_ids) === false);
 // The array should remain unmodified
 var_dump($bad_object_ids);
+try {
+	snmpget($hostname, "", [0 => new stdClass()]);
+} catch (Throwable $e) {
+	echo $e->getMessage();
+}
 ?>
 --EXPECTF--
 array(4) {
@@ -42,3 +47,4 @@ array(4) {
   [0]=>
   int(0)
 }
+Object of class stdClass could not be converted to string