Fix GH-16266: Passing unknown named parameter may segfault

We must not assume that an internal function has arg_info; that is at
least not given for internal classes implementing the magic `__call()`
method.  In such cases we cannot look up the parameter offset by name,
and raise a fatal error.

Author: cmb69

Zend/tests/gh16266.phpt

@@ -0,0 +1,12 @@
+--TEST--
+GH-16266 (Passing unknown named parameter may segfault)
+--EXTENSIONS--
+zend_test
+--FILE--
+<?php
+$o = new _ZendTestClass();
+var_dump($o->test('a', 'b', c: 'c'));
+?>
+--EXPECTF--
+Fatal error: Uncaught Error: Unknown named parameter $c in %s:%d
+%A

Zend/zend_execute.c

@@ -4945,6 +4945,9 @@ static zend_always_inline uint32_t zend_get_arg_offset_by_name(
 			}
 		}
 	} else {
+		if (fbc->internal_function.arg_info == NULL) {
+			return (uint32_t) -1;
+		}
 		for (uint32_t i = 0; i < num_args; i++) {
 			zend_internal_arg_info *arg_info = &fbc->internal_function.arg_info[i];
 			size_t len = strlen(arg_info->name);