Workaround for GL based UIs not giving up their context

plugins/Common/IldaeilUI.cpp

@@ -294,10 +294,10 @@ public:
         if (fPlugin == nullptr || fPlugin->fCarlaHostHandle == nullptr)
             return;
 
+        fPluginHostWindow.hide();
         if (fDrawingState == kDrawingPluginGenericUI || fDrawingState == kDrawingPluginEmbedUI)
             carla_show_custom_ui(fPlugin->fCarlaHostHandle, 0, false);
 
-        fPluginHostWindow.hide();
     }
 
     void createPluginGenericUI(const CarlaHostHandle handle, const CarlaPluginInfo* const info)

plugins/Common/PluginHostWindow.cpp

@@ -141,6 +141,7 @@ struct PluginHostWindow::PrivateData
 #elif defined(DISTRHO_OS_MAC)
         if (view != nullptr)
             [view setHidden:YES];
+        [NSOpenGLContext clearCurrentContext];
 #elif defined(DISTRHO_OS_WINDOWS)
 #else
         pluginWindow = 0;