Issue with Plot label map

Problem Thank you for provide great library:) I have a problem about plotting LabelMap using plot().

To reproduce

def get_data(args):
    print(f'> Getting {args.mode} data.... > Augmentation mode: {args.transform}')
    data_path = os.path.join(args.data_dir, args.hospital)
    
    dataset = MedicalDataset(root_dir=data_path, args=args)
    for data in dataset.training_set:
        one_subject = data
        label = data['label'][tio.DATA]
        print((data['label'][tio.DATA]== 1).nonzero(as_tuple=True))
        one_subject.plot()
    return dataset

class MedicalDataset(Dataset):
    def __init__(self, root_dir, args):
        self.root_dir = root_dir
        self.image_size = args.image_size

        self.subjects = []
        dicom_list = os.listdir(os.path.join(self.root_dir, 'dicom'))
        for dicom_dir in tqdm(dicom_list):
            
            subject = tio.Subject(
                input=tio.ScalarImage(os.path.join(root_dir, 'dicom', dicom_dir)),
                label=tio.LabelMap(os.path.join(root_dir, 'label', dicom_dir+'.nii.gz')),
            )
            self.subjects.append(subject)

        self.training_set = tio.SubjectsDataset(self.subjects)
        print(f'{args.mode} dataset_size:', len(self.training_set), 'subjects')

Expected behavior Large size of segment is shown on plot but, small size of segment is not shown like "Actual behavior. So I check label category on nii.gz file by printing tensor, but there was no probelm. Does it originally working like this?

Actual behavior

System info

Output of python <(curl -s https://raw.githubusercontent.com/fepegar/torchio/main/print_system.py):

Platform:	Windows-10-10.0.19043-SP0
torchio:	0.18.62
torch:	1.9.1+cu111
numpy:	1.21.2
Python:	3.9.6 | packaged by conda-forge | (default, Jul 11 2021, 03:37:25) [MSC v.1916 64 bit (AMD64)]

[nepersica]

Thank you for your kind answering and fixing problem even though there was a problem talking with me. I wish you every happiness!!☺🌹

[fepegar]

Alright. You discovered a bug. Thanks for reporting and for sharing your data! I will fix it in a second.