panelPart: null guard

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

@@ -220,6 +220,7 @@ export class PanelPart extends CompositePart<Panel> implements IPanelService {
 	}
 
 	private layoutCompositeBar(): void {
+		if (this.dimension) {
 			let availableWidth = this.dimension.width - 8; // take padding into account
 			if (this.toolBar) {
 				// adjust height for global actions showing
@@ -227,6 +228,7 @@ export class PanelPart extends CompositePart<Panel> implements IPanelService {
 			}
 			this.compositeBar.layout(new Dimension(availableWidth, this.dimension.height));
 		}
+	}
 
 	public shutdown(): void {
 		// Persist Hidden State