add check totoggleMainNav so returns if no nav take 2

diff --git a/js/game.js b/js/game.js
index 437f7b6..b86fdea 100644
--- a/js/game.js
+++ b/js/game.js
@@ -305,7 +305,7 @@ function toggleMainNav()
 {
     let game_content = elt('game-content');
     let nav_obj = elt('main-nav');
-    if (nav_obj) {
+    if (!nav_obj) {
         return;
     }
     if ((!nav_obj.style.left && !nav_obj.style.right) ||