try this

Author: ajgeiss0702

src/lib/utils.ts

@@ -149,6 +149,14 @@ export function escapeHtml(unsafe: string)
       .replace(/'/g, "'");
 }
 
+export function isIterable(obj: never) {
+    // checks for null and undefined
+    if (obj == null) {
+        return false;
+    }
+    return typeof obj[Symbol.iterator] === 'function';
+}
+
 
 
 export type HistoricalEntry = {

src/routes/tools/test/productPriority/+page.svelte

@@ -1,6 +1,7 @@
 <script lang="ts">
 
   import {flip} from "svelte/animate";
+  import { isIterable } from "$lib/utils";
 
   export let data;
 
@@ -11,13 +12,14 @@
 
   $: {
     i;
-    for (const product of data.products) {
-      const lastStock = JSON.parse(product.stock);
-      const velocityInfluence = (product.available && product.purchasesPerHour == -1 ? 100 : product.purchasesPerHour) * (Math.random()/2);
-      let distance = (Date.now() - product.stockChecked);
-      if(!product.available && distance > 10) distance *= (Math.random()/32)
-      rankings[product.handle] = ((distance / (3 * 60 * 60e3)) + velocityInfluence) / (lastStock?.total === 0 ? 100 : (lastStock?.total === -1 ? 10 : 1));
-      
+    if(isIterable(data.products as never)) {
+      for (const product of data.products) {
+        const lastStock = JSON.parse(product.stock);
+        const velocityInfluence = (product.available && product.purchasesPerHour == -1 ? 100 : product.purchasesPerHour) * (Math.random()/2);
+        let distance = (Date.now() - product.stockChecked);
+        if(!product.available && distance > 10) distance *= (Math.random()/32)
+        rankings[product.handle] = ((distance / (3 * 60 * 60e3)) + velocityInfluence) / (lastStock?.total === 0 ? 100 : (lastStock?.total === -1 ? 10 : 1));
+      }
     }
 
     sortedRankings = Object.entries(rankings).sort((a, b) => b[1] - a[1]);