warn about uncaught exceptions inside LazyPromise

related to #37221

src/vs/workbench/services/extensions/node/lazyPromise.ts

@@ -5,6 +5,7 @@
 'use strict';
 
 import { TPromise, ValueCallback, ErrorCallback } from 'vs/base/common/winjs.base';
+import { onUnexpectedError } from 'vs/base/common/errors';
 
 export class LazyPromise {
 
@@ -75,6 +76,10 @@ export class LazyPromise {
 
 		if (this._actual) {
 			this._actualErr(err);
+		} else {
+			// If nobody's listening at this point, it is safe to assume they never will,
+			// since resolving this promise is always "async"
+			onUnexpectedError(err);
 		}
 	}