Laravel 获取关系数据

我正在尝试获取关系数据，但Trying to get property 'district_name' of non-object出现错误。我只是在学习laravel。

这是我的模型：

自由学校

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class LibSchool extends Model
{
    function getAllSchool()
    {
        return LibSchool::all();
    }

    public function district()
    {
        return $this->belongsTo('App\LibDistrict');
    }
}

自由区

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use App\LibSchool;

class LibDistrict extends Model
{
    public function schools()
    {
        return $this->hasMany('App\LibSchool');
    }
}

表

控制器

class SchoolController extends Controller
{
    public function index()
    {
        $q = Input::get('q');
        if ($q != "") {
            $schools = LibSchool::where('school_name', 'LIKE', '%' . $q . '%')
                        ->with('district')
                        ->orWhere('school_id', 'LIKE', '%' . $q . '%')
                        ->orWhere('address', 'LIKE', '%' . $q . '%')
                        ->orWhere('school_head', 'LIKE', '%' . $q . '%')
                        ->orWhere('level', 'LIKE', '%' . $q . '%')
                        ->orderBy('school_name', 'asc')
                        ->paginate(15)->appends('q', $q);
        } else {
            $schools = LibSchool::with('district')
                                ->orderBy('school_name', 'asc')
                                ->paginate(15);
        }
        return view('schools.index')->with('data', ['schools' => $schools, 'q' => $q]);
    }
}

看法

<table class="table table-hover table-bordered table-striped">
    <tr>
        <th>School ID</th>
        <th>School NAME</th>
        <th>Address</th>
        <th>School Head</th>
        <th>Level</th>
        <th>Division</th>
        <th>District</th>
    </tr>
    @if($data['schools']->total() > 0)
    @foreach($data['schools'] as $school)
    <tr>
        <td>{{$school->school_id}}</td>
        <td>{{$school->school_name}}</td>
        <td>{{$school->address}}</td>
        <td>{{$school->school_head}}</td>
        <td>{{$school->level}}</td>
        <td>{{$school->district->district_name}}</td>
    </tr>
    @endforeach
    @else
    <td colspan="7" class="text-danger">No records</td>
    @endif
</table>
{{$data['schools']->links()}}