Fix plugin cleanup

Signed-off-by: falkTX <falktx@falktx.com>

src/CardinalPlugin.cpp

@@ -228,17 +228,20 @@ public:
     ~CardinalPlugin() override
     {
         {
-            const ScopedContext sc(this);
+            const MutexLocker cml(context->mutex);
+            rack::contextSet(context);
+
             /*
             delete context->scene;
             context->scene = nullptr;
-
             delete context->event;
             context->event = nullptr;
             */
-            delete context;
         }
 
+        delete context;
+        rack::contextSet(nullptr);
+
         if (! fAutosavePath.empty())
             rack::system::removeRecursively(fAutosavePath);
     }

src/CardinalUI.cpp

@@ -139,6 +139,7 @@ public:
                     if (button->text == "Library")
                     {
                         layout->children.erase(it);
+                        button->parent = nullptr;
                         delete button;
                         break;
                     }