How to resolving error : Trying to get property 'title' of non-object

I want to retrieve the title data from the proposal table, but I always get an error like this

progressReport model :

class ProgressReport extends Model
{
    use HasFactory;
    protected $guarded = ['id'];

    protected $casts = ['precentation' => 'date'];

    const PROGRESS_PATH = 'public/data/Report/Progress';
    const PROGRESS_REPORT = 'Progress';
    const FINAL_REPORT = 'Final';

    public function user()
    {
        return $this->belongsTo(User::class, 'user_id');
    }

    public function proposal()
    {
        return $this->belongsTo(Proposal::class, 'proposal_id');
    }

    public function getPathFile($file)
    {
        $uploadFileName = Str::of($file->getClientOriginalName())->replace(' ', '-');
        $fileName = pathinfo($uploadFileName, PATHINFO_FILENAME);
        $fileExtension = $file->getClientOriginalExtension();
        $name = $fileName . '-' . now()->format('dmyhis') . '.' . $fileExtension;
        $fileUrl = $file->storeAs(ProgressReport::PROGRESS_PATH, $name);
        return $fileUrl;
    }
}

proposal model

class Proposal extends Model
{
    use HasFactory;

    const PROPOSAL_PATH = 'public/data/proposal';
    protected $guarded = ['id'];
	
	public function user()
    {
        return $this->belongsTo(User::class);
    }

	   public function progressReport()
    {
        return $this->hasMany(ProgressReport::class);
    }


}

user model

class User extends Authenticatable
{
    use HasApiTokens, HasFactory, Notifiable;

    const LECTURER = 'Dosen';
    const ADMIN = 'Admin';
    const REVIEWER = 'Reviewer';
    /**
     * The attributes that are mass assignable.
     *
     * @var array<int, string>
     */

    public const LECTURER_PATH = "public/images/Lecturer";
    public const REVIEWER_PATH = "public/images/Reviewer";

    protected $table = 'users';
    protected $guarded = ['id'];
    protected $fillable = ['nidn', 'fullname', 'email', 'password', 'faculty', 'major', 'telp', 'birthdate', 'gender', 'address', 'image'];

public function proposal()
    {
        return $this->hasMany(Proposal::class);
    }

 public function progressReport()
    {
        return $this->hasMany(ProgressReport::class);
    }

}

progressreport controller

protected function store(LecturerReportRequest $request, ProgressReport $progress)
    {
        $this->authorize('isLecturer', auth()->user());

        $data = $request->validated();

        $status = ProgressReport::PROGRESS_REPORT;
        $user_id = auth()->user()->id;
        $fileName = ($request->hasFile('document_report')) ? $data['document_report'] = $progress->getPathFile($request->document_report) : "file not found";

        $data = [
            'fullname' => auth()->user()->fullname,
            'status_report' => $status,
            'document_report' => $fileName,
            'title' => $progress->proposal->title, // error from here
            'proposal_id' => $request->proposal_id, 
            'user_id' => $user_id,
        ];
      
        ProgressReport::create($data);

        Mail::to('[email protected]')->send(new SendProgressMail($data));

        return redirect()->route('lpp.lecturer-progress-report.index')->with('success', 'success!');
    }