fixes #84915

src/vs/base/browser/ui/tree/abstractTree.ts

@@ -1417,8 +1417,13 @@ export abstract class AbstractTree<T, TFilterData, TRef> implements IDisposable
 		return this.view.renderHeight;
 	}
 
-	get firstVisibleElement(): T {
+	get firstVisibleElement(): T | undefined {
 		const index = this.view.firstVisibleIndex;
+
+		if (index < 0 || index >= this.view.length) {
+			return undefined;
+		}
+
 		const node = this.view.element(index);
 		return node.element;
 	}

src/vs/base/browser/ui/tree/asyncDataTree.ts

@@ -422,10 +422,6 @@ export class AsyncDataTree<TInput, T, TFilterData = void> implements IDisposable
 		return this.tree.renderHeight;
 	}
 
-	get firstVisibleElement(): T {
-		return this.tree.firstVisibleElement!.element as T;
-	}
-
 	get lastVisibleElement(): T {
 		return this.tree.lastVisibleElement!.element as T;
 	}

src/vs/workbench/contrib/preferences/browser/settingsEditor2.ts

@@ -555,7 +555,11 @@ export class SettingsEditor2 extends BaseEditor {
 				if (DOM.findParentWithClass(e.relatedTarget, 'settings-editor-tree')) {
 					if (this.settingsTree.scrollTop > 0) {
 						const firstElement = this.settingsTree.firstVisibleElement;
-						this.settingsTree.reveal(firstElement, 0.1);
+
+						if (typeof firstElement !== 'undefined') {
+							this.settingsTree.reveal(firstElement, 0.1);
+						}
+
 						return true;
 					}
 				} else {