fixes

database/migrations/2022_06_02_081655_referral_code.php

@@ -20,7 +20,7 @@ class ReferralCode extends Migration
             $table->string('referral_code')->lenght(8)->nullable();
         });
 
-        $existing_user = User::where('referral_code', '')->get();
+        $existing_user = User::where('referral_code', '')->orWhere('referral_code', NULL)->get();
 
         foreach ($existing_user as $user) {
             $random = STR::random(8);

database/migrations/2022_06_02_091921_table-user-referrals.php

@@ -16,8 +16,8 @@ class TableUserReferrals extends Migration
         Schema::create('user_referrals', function (Blueprint $table) {
             $table->unsignedBigInteger('referral_id');
             $table->unsignedBigInteger('registered_user_id');
-            $table->foreign('referral_id')->references('id')->on('users');
-            $table->foreign('registered_user_id')->references('id')->on('users');
+            $table->foreign('referral_id')->references('id')->on('users')->onDelete('cascade');;
+            $table->foreign('registered_user_id')->references('id')->on('users')->onDelete('cascade');;
             $table->timestamps();
         });