<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateChannelTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('channels', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name', 64);
            $table->string('password');
            $table->unsignedInteger('creator_id')->index();
            $table->boolean('hidden')->default(false);
            $table->string('image_url');
            $table->timestamps();

            $table->foreign('creator_id')->references('id')->on('users')->onDelete('cascade');

        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::drop('channels');
    }
}

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateChannelTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('channels', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name', 64);
            $table->string('password')->nullable();
            $table->unsignedInteger('creator_id')->index();
            $table->boolean('hidden')->default(false);
            $table->string('image_url')->nullable();
            $table->timestamps();

            $table->foreign('creator_id')->references('id')->on('users')->onDelete('cascade');

        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::drop('channels');
    }
}

Make nullable fields in channels schema
[*] Make nullable fields in channels schema
