fixes #5148

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

@@ -824,7 +824,7 @@ export class DebugService extends ee.EventEmitter implements debug.IDebugService
 	public revealRepl(focus = true): TPromise<void> {
 		return this.panelService.openPanel(debug.REPL_ID, focus).then((repl: Repl) => {
 			const elements = this.model.getReplElements();
-			if (elements.length > 0) {
+			if (repl && elements.length > 0) {
 				return repl.reveal(elements[elements.length - 1]);
 			}
 		});