Rethrow exceptions in fiber destructor

We need to make sure that HANDLE_EXCEPTION is set when the fiber
throws during destruction.

Fixes oss-fuzz #33875.

Author: nikic

Zend/tests/fibers/throw-during-fiber-destruct.phpt

@@ -0,0 +1,21 @@
+--TEST--
+Make sure exceptions are rethrown when throwing from fiber destructor
+--FILE--
+<?php
+$fiber = new Fiber(function() {
+    try {
+        Fiber::suspend();
+    } finally {
+        throw new Exception("Exception 2");
+    }
+});
+$fiber->start();
+unset($fiber);
+throw new Exception("Exception 1");
+?>
+--EXPECTF--
+Fatal error: Uncaught Exception: Exception 2 in %s:%d
+Stack trace:
+#0 [internal function]: {closure}()
+#1 {main}
+  thrown in %s on line %d

Zend/zend_fibers.c

@@ -398,6 +398,11 @@ static void zend_fiber_object_destroy(zend_object *object)
 	zend_fiber_switch_to(fiber);
 
 	if (EG(exception)) {
+		if (!exception && EG(current_execute_data) && EG(current_execute_data)->func
+				&& ZEND_USER_CODE(EG(current_execute_data)->func->common.type)) {
+			zend_rethrow_exception(EG(current_execute_data));
+		}
+
 		zend_exception_set_previous(EG(exception), exception);
 
 		if (EG(flags) & EG_FLAGS_IN_SHUTDOWN) {