refactor(main.ts): improve code readability by adding conditional check for ijs length before initializing stage or collection

fix(resources.ts): handle case when imagesJson element is not found to prevent error and return empty array

assets/ts/resources.ts

@@ -9,7 +9,10 @@ export interface ImageJSON {
 }
 
 export function initResources(): ImageJSON[] {
-  const imagesJson = document.getElementById('imagesSource') as HTMLScriptElement
+  const imagesJson = document.getElementById('imagesSource')
+  if (!imagesJson) {
+    return []
+  }
   return JSON.parse(imagesJson.textContent as string).sort(
     (a: ImageJSON, b: ImageJSON) => {
       if (a.index < b.index) {