add test on uninstallation of exception filter

tests/exception_filter_005.phpt

@@ -0,0 +1,53 @@
+--TEST--
+Test V8::setExceptionFilter() : Uninstall filter on NULL
+--SKIPIF--
+<?php require_once(dirname(__FILE__) . '/skipif.inc'); ?>
+--FILE--
+<?php
+class myv8 extends V8Js
+{
+	public function throwException(string $message) {
+		throw new Exception($message);
+	}
+}
+
+$v8 = new myv8();
+$v8->setExceptionFilter(function (Throwable $ex) {
+	echo "exception filter called.\n";
+	return "moep";
+});
+
+$v8->executeString('
+	try {
+		PHP.throwException("Oops");
+	}
+	catch (e) {
+		var_dump(e);
+	}
+', null, V8Js::FLAG_PROPAGATE_PHP_EXCEPTIONS);
+
+$v8->setExceptionFilter(null);
+
+try {
+        $v8->executeString('
+                try {
+                        PHP.throwException("Oops");
+                        print("done\\n");
+                }
+                catch (e) {
+                        print("caught\\n");
+                        var_dump(e.getMessage());
+                }
+        ', null, V8Js::FLAG_PROPAGATE_PHP_EXCEPTIONS);
+} catch (Exception $ex) {
+        echo "caught in php: " . $ex->getMessage() . PHP_EOL;
+}
+
+?>
+===EOF===
+--EXPECT--
+exception filter called.
+string(4) "moep"
+caught
+string(4) "Oops"
+===EOF===