fixes #40022

src/vs/workbench/parts/debug/browser/debugViewlet.ts

@@ -59,7 +59,6 @@ export class DebugViewlet extends PersistentViewsViewlet {
 
 		const el = parent.getHTMLElement();
 		DOM.addClass(el, 'debug-viewlet');
-		this.updateBreakpointsMaxSize();
 	}
 
 	public focus(): void {
@@ -116,6 +115,7 @@ export class DebugViewlet extends PersistentViewsViewlet {
 		// attach event listener to
 		if (panel.id === BREAKPOINTS_VIEW_ID) {
 			this.breakpointView = panel;
+			this.updateBreakpointsMaxSize();
 		} else {
 			this.panelListeners.set(panel.id, panel.onDidChange(() => this.updateBreakpointsMaxSize()));
 		}
@@ -128,9 +128,11 @@ export class DebugViewlet extends PersistentViewsViewlet {
 	}
 
 	private updateBreakpointsMaxSize(): void {
-		// We need to update the breakpoints view since all other views are collapsed #25384
-		const allOtherCollapsed = this.views.every(view => !view.isExpanded() || view === this.breakpointView);
-		this.breakpointView.maximumBodySize = allOtherCollapsed ? Number.POSITIVE_INFINITY : this.breakpointView.minimumBodySize;
+		if (this.breakpointView) {
+			// We need to update the breakpoints view since all other views are collapsed #25384
+			const allOtherCollapsed = this.views.every(view => !view.isExpanded() || view === this.breakpointView);
+			this.breakpointView.maximumBodySize = allOtherCollapsed ? Number.POSITIVE_INFINITY : this.breakpointView.minimumBodySize;
+		}
 	}
 }