fix: refresh tests button causing error (microsoft#187948)

Fixes microsoft#187770

Author: connor4312

src/vs/workbench/contrib/testing/browser/testExplorerActions.ts

@@ -1421,7 +1421,7 @@ export class RefreshTestsAction extends Action2 {
 		const testService = accessor.get(ITestService);
 		const progressService = accessor.get(IProgressService);
 
-		const controllerIds = distinct(elements.map(e => e.test.controllerId));
+		const controllerIds = distinct(elements.filter(isDefined).map(e => e.test.controllerId));
 		return progressService.withProgress({ location: Testing.ViewletId }, async () => {
 			if (controllerIds.length) {
 				await Promise.all(controllerIds.map(id => testService.refreshTests(id)));