add nullable parent_id

database/migrations/2022_10_31_100142_create_product_categories_table.php

@@ -18,7 +18,7 @@ public function up()
             $table->id();
             $table->string('name');
             $table->string('image');
-            $table->unsignedInteger('parent_id');
+            $table->unsignedInteger('parent_id')->nullable();
             $table->unsignedTinyInteger('status')->default(ProductCategory::STATUS_ENABLE);
             $table->unsignedInteger('ordering');
             $table->softDeletes();

database/migrations/2022_10_31_100202_create_post_categories_table.php

@@ -18,7 +18,7 @@ public function up()
             $table->id();
             $table->string('name');
             $table->string('image');
-            $table->unsignedInteger('parent_id');
+            $table->unsignedInteger('parent_id')->nullable();
             $table->unsignedTinyInteger('status')->default(PostCategory::STATUS_ENABLE);
             $table->unsignedInteger('ordering');
             $table->softDeletes();