Laravel Edit removes uploaded file

I am creating a Laravel crud. in here i have a DB table called:
File:
‘title’,’description_short’,’description_long,’file’,’language’

the problem lays in the ‘file’ column. here i can upload files like word and excel. but whenever i edit a row with a file attached. the file gets removed if i don’t upload A or THE file again.

edit.blade:

<div class="row">
    <div class="col-sm-8 offset-sm-2">
        <h1 class="display-3"> {{('Editing files')}}</h1>

        @if ($errors->any())
        <div class="alert alert-danger">
            <ul>
                @foreach ($errors->all() as $error)
                <li>{{ $error }}</li>
                @endforeach
            </ul>
        </div>
        <br />
        @endif

        @if(empty($fileEdit))
        <div>{{('Choose file to edit')}}</div>
        @else
        <form method="post" action="{{ route('admin.file.update', $fileEdit->id) }}">
            @method('PUT')
            @csrf
            <div class="form-group">

                <label for="name">{{('title')}}</label>
                <input type="text" class="form-control" name="title" value="{{ $fileEdit->title }}" />
            </div>
            <div class="form-group">

                <label for="name"> {{('Short description')}}</label>
                <input type="text" class="form-control" name="description_short" value="{{ $fileEdit->description_short }}" />
            </div>
            <div class="form-group">

                <label for="name"> {{('Long description')}}</label>
                <input type="text" class="form-control" name="description_long" value="{{ $fileEdit->description_long }}" />
            </div>
            <div class="form-group">

                <label for="name"> {{('file')}}</label>
                <input type="file" class="form-control" name="file" value="{{ $fileEdit->file }}" />
            </div>
            <div class="form-group">
                <label for="name">{{('language')}}</label>
                <select name="language_id" class="form-control">
                    @foreach($languages as $language)
                    <option value=" {{$language->id}}">{{$language->name}}</option>
                    @endforeach
                </select>
            </div>

            <button type="submit" class="btn btn-primary">Update</button>
        </form>

        @endif
    </div>
</div>

controller:

<?php

namespace AppHttpControllersadmin;

use AppHttpControllersController;
use IlluminateHttpRequest;
use AppModelsFile;
use AppModelsLanguage;


class FileController extends Controller
{

    public function index()
    {
        $files = File::with('language')->get();
        $languages = Language::all();
        return view('admin.file.index', compact('files', 'languages'));
    }

  
    public function create()
    {
        //
    }

   
    public function store(Request $request)
    {
        $request->validate([
            'title'=>'required',
            'description_short'=>'',
            'description_long'=>'',
            'file'=>'',
            'language_id'=> [
                'required', 'exists:language,id'
            ],
        ]);

        $file = new File([
            'title'=> $request->get('title'),
            'description_short'=> $request->get('description_short'),
            'description_long'=> $request->get('description_long'),
            'file'=>$request->get('file'),
            'language_id'=> $request->language_id,
        ]);
        $file->save();
        return back();
    }

    public function show($id)
    {
        //
    }

 
    public function edit($id)
    {
        $files = File::all();
        $fileEdit = File::find($id);
        $languages = Language::all();
        return view('admin.file.index', compact('files', 'fileEdit', 'languages'));
    }

  
    public function update(Request $request, $id)
    {
        $request->validate([
            'title'=>'required',
            'description_short'=>'',
            'description_long'=>'',
            'file'=>'',
            'language_id'=> [
                'required', 'exists:language,id'
            ],
        ]);

        $fileData =  [
            'title'=> $request->title,
            'description_short'=> $request->description_short,
            'description_long'=> $request->description_long,
            'file'=>$request->file,
            'language_id'=> $request->language_id,
        ];
        File::whereId($id)->update($fileData);
        return redirect()->route('admin.file.index');
    }
    
    public function destroy($id)
    {
    $file = File::find($id);
    $file->delete();
    return redirect()->route('admin.file.index');
    }
}

File model:

<?php

namespace AppModels;

use IlluminateDatabaseEloquentFactoriesHasFactory;
use IlluminateDatabaseEloquentModel;

class File extends Model
{
    use HasFactory;

    public function language(){
        return $this->belongsTo(Language::class);
    }
    protected $table = 'file';
    protected $fillable = [
        'title',
        'description_short',
        'description_long',
        'file',
        'language_id',
        'user_id',
    ];
}