AttributeError: 'NoneType' object has no attribute 'isoformat'

I got this error when I tried to open the model in the admin panel
File "..../venv/lib/python3.8/site-packages/gino_admin/utils.py", line 304, in get_obj_id_from_row
result[x] = row[x].isoformat()
AttributeError: 'NoneType' object has no attribute 'isoformat'

model

class Notification(db.Model):
......
created_at = db.Column(
sa.DateTime,
nullable=False,
server_default=sa.func.now(),
)

read_at = db.Column(sa.DateTime, nullable=True)

The error occurs for the read_at field, since it can be None

gino-admin/gino_admin/utils.py

Line 304 in 1789d63

result[x] = row[x].isoformat()

@alexeydad1, hi thanks for opening the issue, but I'm not sure when I can fix it, library in low priority for me right now, but if you want - you can open the PR and I will merge it