use apt-btrfs-snapshot without argument returns AttributeError

[Claudius Raphael Paeth]

##Right after install

##of: apt-btrfs-snapshot

:;apt-cache show apt-btrfs-snapshot | grep Version
Version: 3.5.1

##in: Ubuntu 18.04 LTS Bionic Beaver Desktop

:;uname -o -s -r -i -p
Linux 4.15.0-20-generic x86_64 x86_64 GNU/Linux

:;lsb_release -rd
Description: Ubuntu 18.04 LTS
Release: 18.04

##and fixing missing dependencies
##by: installing python3-distutils

:;sudo apt install python3-distutils

## just calling:

:;sudo apt-btrfs-snapshot

## without Arguments|Commands|Attributes

##expected:
:;sudo apt-btrfs-snapshot
supported

##instead returned:

Traceback (most recent call last):
  File "/usr/bin/apt-btrfs-snapshot", line 98, in <module>
    if args.command == "supported":
AttributeError: 'Namespace' object has no attribute 'command'