Fix use-of-uninitialized-value in start_fake_frame

Author: iluuu1994

Zend/zend_execute.c

@@ -5049,7 +5049,7 @@ zval * ZEND_FASTCALL zend_handle_named_arg(
 }
 
 static zend_execute_data *start_fake_frame(zend_execute_data *call, const zend_op *opline) {
-	zend_execute_data *old_prev_execute_data = call->prev_execute_data;
+	zend_execute_data *old_prev_execute_data = ZEND_USER_CODE(call->func->common.type) ? call->prev_execute_data : NULL;
 	call->prev_execute_data = EG(current_execute_data);
 	call->opline = opline;
 	EG(current_execute_data) = call;

Zend/zend_execute_API.c

@@ -897,6 +897,8 @@ zend_result zend_call_function(zend_fcall_info *fci, zend_fcall_info_cache *fci_
 	}
 
 	if (UNEXPECTED(ZEND_CALL_INFO(call) & ZEND_CALL_MAY_HAVE_UNDEF)) {
+		/* zend_handle_undef_args assumes prev_execute_data is initialized for user calls. */
+		call->prev_execute_data = NULL;
 		if (zend_handle_undef_args(call) == FAILURE) {
 			zend_vm_stack_free_args(call);
 			zend_vm_stack_free_call_frame(call);