Fix linting and build errors.

src/app/state/userpathhandler.ts

@@ -4,7 +4,7 @@ import {MazeCell} from "../model/maze.ts";
 
 export default function handleUserClicked(state: State, x: number, y: number): State {
     if (isClickAllowed(x, y, state)) {
-        let maze = state.maze!;
+        const maze = state.maze!;
         // Okay, we clicked a cell that's adjacent to the end of the userpath (or which IS the end of the userpath)
         // and that's not blocked by a wall. Now let's see.
         if (-1 === state.userPath.findIndex(step => step.x === x && step.y === y)) {