Allow null pointers in IEditController::setComponentHandler

src/common/logging/vst3.cpp

@@ -306,8 +306,13 @@ bool Vst3Logger::log_request(
     const YaEditController::SetComponentHandler& request) {
     return log_request_base(is_host_vst, [&](auto& message) {
         message << request.instance_id
-                << ": IEditController::setComponentHandler(handler = "
-                   "<IComponentHandler*>)";
+                << ": IEditController::setComponentHandler(handler = ";
+        if (request.component_handler_proxy_args) {
+            message << "<IComponentHandler*>";
+        } else {
+            message << "<nullptr>";
+        }
+        message << ")";
     });
 }
 

src/common/serialization/vst3/plugin/edit-controller.h

@@ -344,12 +344,19 @@ class YaEditController : public Steinberg::Vst::IEditController {
 
         native_size_t instance_id;
 
-        Vst3ComponentHandlerProxy::ConstructArgs component_handler_proxy_args;
+        /**
+         * Some hosts will pass a null pointer to explicitly free the component
+         * handler passed before releasing the object instance. This also
+         * happens in the SDK, so this seems like valid behaviour we should
+         * support.
+         */
+        std::optional<Vst3ComponentHandlerProxy::ConstructArgs>
+            component_handler_proxy_args;
 
         template <typename S>
         void serialize(S& s) {
             s.value8b(instance_id);
-            s.object(component_handler_proxy_args);
+            s.ext(component_handler_proxy_args, bitsery::ext::StdOptional{});
         }
     };