The image must be an image - php

Question

So here it is.
I want to edit a data in database, it work perfectly if I upload an image every time I fill the form. but the problem raised when I edited another data and didn't upload an image instead of filling it with old image data (which is the file in my local) from database which is a string. the image validation makes the error was raised.
here my image validation
'image' => 'image|max:1024'
if I just put it like this 'image' => 'max:1024', it will run well because it wouldn't check if it's an image, but it will generate a problem where user start using edit data function to inject another unwanted code.
here is the update code
use WithFileUploads;
public $productId;
public $title;
public $description;
public $price;
public $image;
public $imageOld;
protected $listeners = [
'editProduct' => 'editProductHandler'
];
public function update()
{
$this->validate([
'title' => 'required|min:3',
'price' => 'required|numeric',
'description' => 'required|max:180',
'image' => 'image|max:1024'
]);
if ($this->productId) {
$product = Product::find($this->productId);
$image = '';
if ($this->image) {
Storage::disk('public')->delete($product->image);
$imageName = \Str::slug($this->title, '-')
. '-'
. uniqid()
. '.' . $this->image->getClientOriginalExtension();
$this->image->storeAs('public', $imageName, 'local');
$image = $imageName;
} else {
$image = $product->image;
}
$product->update([
'title' => $this->title,
'price' => $this->price,
'description' => $this->description,
'image' => $image
]);
$this->emit('productUpdated');
}
}