Laravel issue on passing image data

I'm trying to upload image for an icon image on my project. When POST this function i receive and error says

Laravel created by does not have a default value

when I already add the created_by field on my data list, below is my code :

public function postAddProject($dev_id)
    {
        $data = request()->validate([
            'name' => 'required',
            'address' => 'required|max:100',
            'address2' => 'required_with:address3|max:100',
            'address3' => 'nullable|max:100',
            'zipcode' => 'required|numeric|digits:5',
            'attachment' => 'mimes:jpeg,png'
        ]);

        $data['developer_id'] = $dev_id;
        $data['status'] = 'active';
        $data['created_by'] = auth()->user()->id;

        $project = Project::create($data);

        if (!empty($data['attachment'])) {
            $attachment_file = $data['attachment'];
            $logo_file_contents = file_get_contents($attachment_file);
            $imageData = [
                'data' => $logo_file_contents,
                'mime_type' => $attachment_file->getClientMimeType(),
                'size' => mb_strlen($logo_file_contents),
                'extension' => $attachment_file->getClientOriginalExtension()
            ];

            // $imageData = self::optimizeImage($imageData);

            $imageMedia = Media::create([
                'category' => 'project-icon',
                'mimetype' => $imageData['mime_type'],
                'data' => $imageData['data'],
                'size' => $imageData['size'],
                'created_by' => auth()->user()->id,
                'filename' => 'project_' . date('Y-m-d_H:i:s') . "." . $imageData['extension']
            ]);

            $project->logo_media()->associate($imageMedia);
            $project->save();
        }

        $dev_id = $project->developer_id;

        return redirect()->route('admin.developers.projects.index', ['dev_id' => $dev_id])->withStatus(__('Admin successfully created.'));
    }

via Chebli Mohamed