rework logic of setting selectedItems in multi-select mode

Author: TylerLeonhardt

src/vs/base/parts/quickinput/browser/quickInput.ts

@@ -818,9 +818,15 @@ class QuickPick<T extends IQuickPickItem> extends QuickInput implements IQuickPi
 			}));
 			this.visibleDisposables.add(this.ui.onDidAccept(() => {
 				if (this.canSelectMany) {
-					this._selectedItems = this.ui.list.getCheckedElements() as T[];
-					this.onDidChangeSelectionEmitter.fire(this.selectedItems);
+					// if there are no checked elements, it means that an onDidChangeSelection never fired to overwrite
+					// `_selectedItems`. In that case, we should emit one with an empty array to ensure that
+					// `.selectedItems` is up to date.
+					if (!this.ui.list.getCheckedElements().length) {
+						this._selectedItems = [];
+						this.onDidChangeSelectionEmitter.fire(this.selectedItems);
+					}
 				} else if (this.activeItems[0]) {
+					// For single-select, we set `selectedItems` to the item that was accepted.
 					this._selectedItems = [this.activeItems[0]];
 					this.onDidChangeSelectionEmitter.fire(this.selectedItems);
 				}