bindings: Add empty checks for toV8()

Source/bindings/core/v8/ScriptPromiseProperty.h

Index: Source/bindings/core/v8/ScriptPromiseProperty.h
diff --git a/Source/bindings/core/v8/ScriptPromiseProperty.h b/Source/bindings/core/v8/ScriptPromiseProperty.h
index 7d4d199fcae9ac4f8ca4e3a5da163784e78e8427..da166e9f6d574a2e42c051a880c55b58c5203e41 100644
--- a/Source/bindings/core/v8/ScriptPromiseProperty.h
+++ b/Source/bindings/core/v8/ScriptPromiseProperty.h
@@ -120,6 +120,8 @@ template<typename HolderType, typename ResolvedType, typename RejectedType>
 v8::Local<v8::Object> ScriptPromiseProperty<HolderType, ResolvedType, RejectedType>::holder(v8::Isolate* isolate, v8::Local<v8::Object> creationContext)
 {
     v8::Local<v8::Value> value = toV8(m_holder, creationContext, isolate);
+    if (value.IsEmpty())
+        return v8::Local<v8::Object>();
     return value.As<v8::Object>();
 }