fixes #13867

src/vs/workbench/services/files/electron-browser/fileService.ts

@@ -87,11 +87,11 @@ export class FileService implements IFileService {
 		this.registerListeners();
 	}
 
-	private onFileServiceError(msg: string): void {
+	private onFileServiceError(msg: any): void {
 		errors.onUnexpectedError(msg);
 
 		// Detect if we run < .NET Framework 4.5
-		if (msg && msg.indexOf(FileService.NET_VERSION_ERROR) >= 0 && !this.storageService.getBoolean(FileService.NET_VERSION_ERROR_IGNORE_KEY, StorageScope.WORKSPACE)) {
+		if (typeof msg === 'string' && msg.indexOf(FileService.NET_VERSION_ERROR) >= 0 && !this.storageService.getBoolean(FileService.NET_VERSION_ERROR_IGNORE_KEY, StorageScope.WORKSPACE)) {
 			this.messageService.show(Severity.Warning, <IMessageWithAction>{
 				message: nls.localize('netVersionError', "The Microsoft .NET Framework 4.5 is required. Please follow the link to install it."),
 				actions: [