Fix mem leak

Author: Girgias

Zend/tests/offsets/null_offset_dep_promoted.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Do not leak when promoting null offset deprecation
+--FILE--
+<?php
+
+set_error_handler(function ($errno, $errstr) {
+    throw new Exception($errstr);
+});
+
+try {
+	$a = ['foo' => 'bar', null => new stdClass];
+} catch (Throwable $e) {
+	echo $e::class, ': ', $e->getMessage(), PHP_EOL;
+}
+?>
+--EXPECT--
+Exception: Using null as an array offset is deprecated, use an empty string instead

Zend/zend_vm_def.h

@@ -6281,6 +6281,7 @@ ZEND_VM_C_LABEL(num_index):
 		} else if (UNEXPECTED(Z_TYPE_P(offset) == IS_NULL)) {
 			zend_error(E_DEPRECATED, "Using null as an array offset is deprecated, use an empty string instead");
 			if (UNEXPECTED(EG(exception))) {
+				zval_ptr_dtor_nogc(expr_ptr);
 				HANDLE_EXCEPTION();
 			}
 			str = ZSTR_EMPTY_ALLOC();