fix listener leaks (#17913)

* fix listener leaks

* add null check

* simplify

* pr comments

src/sql/workbench/contrib/objectExplorer/browser/serverTreeView.ts

@@ -276,6 +276,7 @@ export class ServerTreeView extends Disposable implements IServerTreeView {
 				if (profile) {
 					newProfile = profile;
 				}
+				groups.forEach(group => group.dispose());
 			}
 
 			const currentSelections = this._tree!.getSelection();