you should change your validation
in STORE function, you should give an image and upload it (if it is required)
but in UPDATE function maybe the user does’nt want to change image and user only wants to change for exmaple just the name, so user can select no image in update
so your validation in UPDATE must be NULLABLE.

        $this->validate($request,[
            'name' => 'required',
            'image' => 'nullable|mimes:jpeg,bmp,png,jpg'
        ]);

//Here is my edit form (image field)
I have an edit form which has an image field where a user can upload a new image if he wants to.

But if the user does not upload a new photo I want to just use the photo that’s already in the database. And not update the image field at all. But in my code whenever I am trying to without uploading new image form is not taking the old input value.

<div class="form-group">
   <input type="file" name="image">
 </div>

//this is the update function

 public function update(Request $request, $id)
    {
        $this->validate($request,[
            'name' => 'required',
            'image' => 'mimes:jpeg,bmp,png,jpg'
        ]);
        // get form image
        $image = $request->file('image');
        $slug = str_slug($request->name);
        $category = Category::find($id);
        if (isset($image))
        {
//            make unique name for image
            $currentDate = Carbon::now()->toDateString();
            $imagename = $slug.'-'.$currentDate.'-'.uniqid().'.'.$image->getClientOriginalExtension();
//            check category dir is exists
            if (!Storage::disk('public')->exists('category'))
            {
                Storage::disk('public')->makeDirectory('category');
            }
//            delete old image
            if (Storage::disk('public')->exists('category/'.$category->image))
            {
                Storage::disk('public')->delete('category/'.$category->image);
            }
//            resize image for category and upload
            $categoryimage = Image::make($image)->resize(1600,479)->stream();
            Storage::disk('public')->put('category/'.$imagename,$categoryimage);
            //            check category slider dir is exists
            if (!Storage::disk('public')->exists('category/slider'))
            {
                Storage::disk('public')->makeDirectory('category/slider');
            }
            //            delete old slider image
            if (Storage::disk('public')->exists('category/slider/'.$category->image))
            {
                Storage::disk('public')->delete('category/slider/'.$category->image);
            }
            //            resize image for category slider and upload
            $slider = Image::make($image)->resize(500,333)->stream();
            Storage::disk('public')->put('category/slider/'.$imagename,$slider);
        } else {
            $imagename = $category->image;
        }
        $category->name = $request->name;
        $category->slug = $slug;
        $category->image = $imagename;
        $category->save();
        Toastr::success('Category Successfully Updated :)' ,'Success');
        return redirect()->route('admin.category.index');
    }

// When i click on the edit button it shows the No file Chosen it is not displaying the old image ..