How to resolve "Trying to get property 'pros_name' of non object" in laravel?

I have the following foreach loop in my blade which is showing error:

trying to get property 'pros_name' of non-object

How do I resolve it?

@foreach ($reports as $report)
    <tr>
        <td></a></td>
        <td></td>
 @if($report->book_date== null || ($report->book_date != null && ($report->release_date != null && $report->release_date < date('Y-m-d'))))
        <td class="text-danger"><strong>Vacant</strong></td>
        <td></td>
                                <td>---</td>
                                <td></td>
                                @endif
                                @if($report->book_date != null && ( $report->release_date ==null || $report->release_date >= date('Y-m-d')))
                                    @php 
                                        $doc = DB::table('gen_resident_room')
                                            ->Join('sales_pipeline', 'gen_resident_room.person_id', '=', 'sales_pipeline.id')
                                            ->where([['room_id',$report->room_id]])->first();
                                            $n = explode (",",$doc->pros_name); //error
                                    @endphp
                                    @if($doc->stage === "MoveIn")
                                        <td class="text-success"><b>Occupied</b></td>
                                    @else
                                        <td class="text-success"><b>Booked</b></td>
                                    @endif
                                    <td></td>
                                    <td></td>
                                    <td>  </td>
                                @endif
                            </tr>
                            @endforeach

via Chebli Mohamed