tree: scroll position is 1 if scrolled all the way

fixes #40899

src/vs/base/parts/tree/browser/treeView.ts

@@ -826,7 +826,7 @@ export class TreeView extends HeightMap {
 
 	public getScrollPosition(): number {
 		const height = this.getTotalHeight() - this.viewHeight;
-		return height <= 0 ? 0 : this.scrollTop / height;
+		return height <= 0 ? 1 : this.scrollTop / height;
 	}
 
 	public setScrollPosition(pos: number): void {

src/vs/workbench/parts/debug/electron-browser/repl.ts

@@ -118,7 +118,7 @@ export class Repl extends Panel implements IPrivateReplService {
 				this.refreshTimeoutHandle = null;
 				const previousScrollPosition = this.tree.getScrollPosition();
 				this.tree.refresh().then(() => {
-					if (previousScrollPosition === 1 || previousScrollPosition === 0) {
+					if (previousScrollPosition === 1) {
 						// Only scroll if we were scrolled all the way down before tree refreshed #10486
 						this.tree.setScrollPosition(1);
 					}