Fix error messag bug and imporve test case (#52698)

src/vs/workbench/parts/extensions/electron-browser/extensionTipsService.ts

@@ -208,7 +208,7 @@ export class ExtensionTipsService extends Disposable implements IExtensionTipsSe
 	}
 
 	getWorkspaceRecommendations(): TPromise<string[]> {
-		if (!this.isEnabled) { return TPromise.as([]); }
+		if (!this.isEnabled()) { return TPromise.as([]); }
 
 		return this.fetchCombinedExtensionRecommendationConfig()
 			.then(content => {

src/vs/workbench/parts/extensions/test/electron-browser/extensionsTipsService.test.ts

@@ -301,8 +301,11 @@ suite('ExtensionsTipsService Test', () => {
 	}
 
 	test('ExtensionTipsService: No Prompt for valid workspace recommendations when galleryService is absent', () => {
-		instantiationService.stub(IExtensionGalleryService, 'isEnabled', false);
-		return testNoPromptOrRecommendationsForValidRecommendations(mockTestData.validRecommendedExtensions);
+		const galleryQuerySpy = sinon.spy();
+		instantiationService.stub(IExtensionGalleryService, { query: galleryQuerySpy, isEnabled: () => false });
+
+		return testNoPromptOrRecommendationsForValidRecommendations(mockTestData.validRecommendedExtensions)
+			.then(() => assert.ok(galleryQuerySpy.notCalled));
 	});
 
 	test('ExtensionTipsService: No Prompt for valid workspace recommendations during extension development', () => {