fix(admin): handle null sales channel references in product list and detail views (#15009)

## What

Fixes a crash in the Admin UI when a product has orphaned sales channel references (i.e., the sales channel was deleted but the product association was not cleaned up).

## Why

When a sales channel is deleted, the join table entries linking it to products are not always cleaned up. This results in the API returning `null` entries in the product's `sales_channels` array:

```json
{
  "sales_channels": [null]
}
```

The Admin UI attempts to access `sales_channel.name` without null checks, causing:
```
TypeError: Cannot read properties of null (reading 'name')
```

This crashes both the product list page and the product detail page.

## How

Added defensive null filtering in two components:

1. **`SalesChannelsCell`** (product list table): Filters out `null`/`undefined` entries from the `salesChannels` array before rendering. Uses a TypeScript type guard to maintain type safety.

2. **`ProductSalesChannelSection`** (product detail page): Filters out `null`/`undefined` entries before mapping sales channels for display.

Both components now gracefully handle orphaned references by simply excluding them from the rendered output, showing only valid sales channels.

## Testing

- Product with all valid sales channels → renders normally (no change)
- Product with `sales_channels: [null]` → shows placeholder instead of crashing
- Product with mix of valid and null channels → shows only valid channels
- Product with `sales_channels: []` or `null` → shows placeholder (existing behavior, unchanged)

Fixes #14945


---

> [!NOTE]
> **Low Risk**
> Low risk UI-only change that adds defensive null filtering to prevent runtime crashes when the API returns orphaned `sales_channels` entries; behavior change is limited to hiding invalid entries.
> 
> **Overview**
> Prevents Admin UI crashes when products contain orphaned `sales_channels` entries returned as `null`.
> 
> Adds defensive filtering in the product list `SalesChannelsCell` and product detail `ProductSalesChannelSection` so only non-null sales channels are rendered (falling back to existing placeholder/empty states). Includes a patch changeset for `@medusajs/dashboard`.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit 75478bf. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup>

Author: Vitalini

.changeset/fix-orphaned-sales-channel.md

@@ -0,0 +1,5 @@
+---
+"@medusajs/dashboard": patch
+---
+
+fix(admin): handle null sales channel references in product list and detail views

packages/admin/dashboard/src/components/table/table-cells/product/sales-channels-cell/sales-channels-cell.tsx

@@ -13,39 +13,45 @@ export const SalesChannelsCell = ({
 }: SalesChannelsCellProps) => {
   const { t } = useTranslation()
 
-  if (!salesChannels || !salesChannels.length) {
+  // Filter out null/undefined entries that can occur when a sales channel
+  // is deleted but the product association is not cleaned up
+  const validChannels = salesChannels?.filter(
+    (sc): sc is SalesChannelDTO => sc != null
+  )
+
+  if (!validChannels || !validChannels.length) {
     return <PlaceholderCell />
   }
 
-  if (salesChannels.length > 2) {
+  if (validChannels.length > 2) {
     return (
       <div className="flex h-full w-full items-center gap-x-1 overflow-hidden">
         <span className="truncate">
-          {salesChannels
+          {validChannels
             .slice(0, 2)
             .map((sc) => sc.name)
             .join(", ")}
         </span>
         <Tooltip
           content={
             <ul>
-              {salesChannels.slice(2).map((sc) => (
+              {validChannels.slice(2).map((sc) => (
                 <li key={sc.id}>{sc.name}</li>
               ))}
             </ul>
           }
         >
           <span className="text-xs">
             {t("general.plusCountMore", {
-              count: salesChannels.length - 2,
+              count: validChannels.length - 2,
             })}
           </span>
         </Tooltip>
       </div>
     )
   }
 
-  const channels = salesChannels.map((sc) => sc.name).join(", ")
+  const channels = validChannels.map((sc) => sc.name).join(", ")
 
   return (
     <div className="flex h-full w-full items-center overflow-hidden max-w-[250px]">

packages/admin/dashboard/src/routes/products/product-detail/components/product-sales-channel-section/product-sales-channel-section.tsx

@@ -16,11 +16,15 @@ export const ProductSalesChannelSection = ({
   const { count } = useSalesChannels()
   const { t } = useTranslation()
 
+  // Filter out null/undefined entries that can occur when a sales channel
+  // is deleted but the product association is not cleaned up
   const availableInSalesChannels =
-    product.sales_channels?.map((sc) => ({
-      id: sc.id,
-      name: sc.name,
-    })) ?? []
+    product.sales_channels
+      ?.filter((sc) => sc != null)
+      .map((sc) => ({
+        id: sc.id,
+        name: sc.name,
+      })) ?? []
 
   const firstChannels = availableInSalesChannels.slice(0, 3)
   const restChannels = availableInSalesChannels.slice(3)