clean up after ourselves when the plugin is disabled

main.js

@@ -23,6 +23,11 @@ module.exports = class RibbonOrderLock extends Plugin {
     });
   }
 
+  onunload() {
+    this.observer?.disconnect();
+    this.app.workspace.leftRibbon.onChange = this.originalOnChange;
+  }
+
   observeRibbon() {
     const ribbon = this.app.workspace.leftRibbon;
     const containerEl = ribbon.ribbonItemsEl;