Fixing strict init errors in webview code

#78168

src/vs/workbench/api/common/extHostWebview.ts

@@ -18,7 +18,7 @@ import { Disposable } from './extHostTypes';
 type IconPath = URI | { light: URI, dark: URI };
 
 export class ExtHostWebview implements vscode.Webview {
-	private _html: string;
+	private _html: string = '';
 	private _isDisposed: boolean = false;
 	private _hasCalledAsWebviewUri = false;
 

src/vs/workbench/contrib/webview/browser/webviewService.ts

@@ -18,7 +18,7 @@ export class WebviewService implements IWebviewService {
 	constructor(
 		@IInstantiationService private readonly _instantiationService: IInstantiationService,
 	) {
-		this._instantiationService.createInstance(WebviewThemeDataProvider);
+		this._webviewThemeDataProvider = this._instantiationService.createInstance(WebviewThemeDataProvider);
 	}
 
 	createWebview(