Fix enum cast AST allocation, again

We always need to allocate space for the three children, and only
don't need one of the zend_ast_zval structures.

Author: nikic

Zend/zend_enum.c

@@ -417,15 +417,14 @@ ZEND_API zend_class_entry *zend_register_internal_enum(
 static zend_ast_ref *create_enum_case_ast(
 		zend_string *class_name, zend_string *case_name, zval *value) {
 	// TODO: Use custom node type for enum cases?
-	size_t num_children = value ? 3 : 2;
-	size_t size = sizeof(zend_ast_ref) + zend_ast_size(num_children)
-		+ num_children * sizeof(zend_ast_zval);
+	size_t size = sizeof(zend_ast_ref) + zend_ast_size(3)
+		+ (value ? 3 : 2) * sizeof(zend_ast_zval);
 	char *p = pemalloc(size, 1);
 	zend_ast_ref *ref = (zend_ast_ref *) p; p += sizeof(zend_ast_ref);
 	GC_SET_REFCOUNT(ref, 1);
 	GC_TYPE_INFO(ref) = GC_CONSTANT_AST | GC_PERSISTENT | GC_IMMUTABLE;
 
-	zend_ast *ast = (zend_ast *) p; p += zend_ast_size(num_children);
+	zend_ast *ast = (zend_ast *) p; p += zend_ast_size(3);
 	ast->kind = ZEND_AST_CONST_ENUM_INIT;
 	ast->attr = 0;
 	ast->lineno = 0;