remove permanently removed composites (microsoft#159462)

Author: sandy081

src/vs/workbench/browser/parts/panel/panelPart.ts

@@ -427,18 +427,20 @@ export abstract class BasePanelPart extends CompositePart<PaneComposite> impleme
 
 	private onDidRegisterExtensions(): void {
 		this.extensionsRegistered = true;
-		this.removeNotExistingComposites();
 
-		this.saveCachedPanels();
-	}
-
-	private removeNotExistingComposites(): void {
+		// hide/remove composites
 		const panels = this.getPaneComposites();
-		for (const { id } of this.getCachedPanels()) { // should this value match viewlet (load on ctor)
+		for (const { id } of this.getCachedPanels()) {
 			if (panels.every(panel => panel.id !== id)) {
-				this.hideComposite(id);
+				if (this.viewDescriptorService.isViewContainerRemovedPermanently(id)) {
+					this.removeComposite(id);
+				} else {
+					this.hideComposite(id);
+				}
 			}
 		}
+
+		this.saveCachedPanels();
 	}
 
 	private hideComposite(compositeId: string): void {