Don't throw if view doesn't exist when visibility false (microsoft#191781)

Author: alexr00

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

@@ -246,6 +246,9 @@ export class ExtHostTreeViews implements ExtHostTreeViewsShape {
 	$setVisible(treeViewId: string, isVisible: boolean): void {
 		const treeView = this.treeViews.get(treeViewId);
 		if (!treeView) {
+			if (!isVisible) {
+				return;
+			}
 			throw new NoTreeViewError(treeViewId);
 		}
 		treeView.setVisible(isVisible);