refactored code

src/utils/Display.js

@@ -28,7 +28,9 @@ export const LoadImage = (mapName) => {
     let background = document.querySelector('.bg-img')
 
     img.onload = function() {
+      if (background) {
         background.src = img.src
+      }
     }
 
     img.onerror = function () {