fix syntax

examples/chess/movement.cm

@@ -10,9 +10,9 @@ var MovementSystem_prototype = {
   tryMove: function (piece, to) {
   if (piece.colour != this.turn) return false;
 
-  // normalise ‘to’ into our hybrid coord
-  var dest = [to.x ?? t[0],
-              to.y ?? to[1]];
+  // normalise 'to' into our hybrid coord
+  var dest = [!is_null(to.x) ? to.x : to[0],
+              !is_null(to.y) ? to.y : to[1]];
 
   if (!this.grid.inBounds(dest)) return false;
   if (!this.rules.canMove(piece, piece.coord, dest, this.grid)) return false;