refactor: 产品导出健壮性修改

app/admin/controller/v1/Product.php

@@ -450,8 +450,10 @@ class Product
             if (!$product_related->isEmpty()) {
                 $related = [];
                 foreach ($product_related as $item) {
+                    if (!empty($item->product)) {
                         $related[$item['product_id']][] = $item->product->spu;
                     }
+                }
                 $products->each(function($product) use($related) {
                     if (empty($related[$product->id])) {
                         return;