fix microsoft#179684

Author: meganrogge

src/vs/workbench/contrib/tasks/browser/abstractTaskService.ts

@@ -2747,7 +2747,16 @@ export abstract class AbstractTaskService extends Disposable implements ITaskSer
 		return true;
 	}
 
+	private async _ensureWorkspaceTasks(): Promise<void> {
+		if (!this._workspaceTasksPromise) {
+			await this.getWorkspaceTasks();
+		} else {
+			await this._workspaceTasksPromise;
+		}
+	}
+
 	private async _runTaskCommand(filter?: string | ITaskIdentifier): Promise<void> {
+		await this._ensureWorkspaceTasks();
 		if (!filter) {
 			return this._doRunTaskCommand();
 		}
@@ -2905,7 +2914,7 @@ export abstract class AbstractTaskService extends Disposable implements ITaskSer
 			title: strings.fetching
 		};
 		const promise = (async () => {
-			await this.getWorkspaceTasks();
+			await this._ensureWorkspaceTasks();
 			let taskGroupTasks: (Task | ConfiguringTask)[] = [];
 
 			async function runSingleTask(task: Task | undefined, problemMatcherOptions: IProblemMatcherRunOptions | undefined, that: AbstractTaskService) {