Clear component cache in unload_main method of SmartEnv class

- Added a line to reset the `_components` property to an empty object in the `unload_main` method, ensuring that the component cache is cleared when unloading collections and options.
- This change improves memory management and prevents potential issues related to stale component references during the unloading process.

smart-environment/smart_env.js

@@ -195,6 +195,7 @@ export class SmartEnv {
   }
 
   unload_main(main_key) {
+    this._components = {}; // clear component cache
     this.unload_collections(main_key);
     this.unload_opts(main_key);
     this[main_key] = null;