店舗削除ロジックの修正

app/Logics/Shop/ShopLogic.php

@@ -37,8 +37,12 @@ class ShopLogic
     {
         $shop->delete();
 
-        foreach ($shop->users as $user) {
-            $user->delete();
+        $users = $shop->users;
+
+        if ($users !== null) {
+            foreach ($shop->users as $user) {
+                $user->delete();
+            }
         }
     }
 }