چگونه null بودن یه فیلد را حل کنیم

کد متد Store

 public function store(Request $request)
    {
       $validation=$this->getValidationFactory()->make($request->all(),[
            'title'=>'required|max:255',
            'content'=>'required',
            'category'=>'required|max:10',
            'image_2'=>'mimes:jpeg,png',
            'image_3'=>'mimes:jpeg,png',
            'image_4'=>'mimes:jpeg,png',
            'image_5'=>'mimes:jpeg,png',
            'image_6'=>'mimes:jpeg,png',
            'image_7'=>'mimes:jpeg,png',
       ]);
       if ($validation->fails()){
           return response()->json(['Message'=>'please feel necessary field'],400);
       }
       $article=new Article();
       $article->title=$request->title;
       $article->content=$request->content;
       $article->category=$request->category;
       $article->image_2=$request->image_2;
       $article->image_3=$request->image_3;
       $article->image_4=$request->image_4;
       $article->image_5=$request->image_5;
       $article->image_6=$request->image_6;
       $article->image_7=$request->image_7;
       if ($article->save()){
           $name='article-'.$article->id.'.'.$request->file('image')->getClientOriginalExtension();
           $request->file('image')->move(public_path('images'),$name);
           $article->image=$name;
           $article->save();
           return response()->json(['Message'=>'saved successfully'],200);
       }
    }

حل شد خوشبختانه -key رو اشتباه وارد کرده بودم