Fixed a potential AudioPluginInstance leak in AudioPluginFormatManager::createPluginInstanceAsync()

modules/juce_audio_processors/format/juce_AudioPluginFormat.cpp

@@ -39,10 +39,10 @@ namespace AudioPluginFormatHelpers
                 : instance (inInstance), error (inError), compCallback (inCompletion), owner (invoker)
             {}
 
-            void messageCallback() override     { compCallback->completionCallback (instance, error); }
+            void messageCallback() override     { compCallback->completionCallback (instance.release(), error); }
 
             //==============================================================================
-            AudioPluginInstance* instance;
+            std::unique_ptr<AudioPluginInstance> instance;
             String error;
             std::unique_ptr<AudioPluginFormat::InstantiationCompletionCallback> compCallback;
             std::unique_ptr<CallbackInvoker> owner;