Error when using chirp and "name-x-char" options

got the following errors when starting with:

memory-channels-processor --source "oevsv-repeater-db" --source "fm-channels-iaru-r1" --band 70cm --band 2m --type "fm" --locator JN88xx --sort distance
--output-file "chirp_fm_2m_70cm.csv" --output-format="chirp" --chirp-name "name-5-char"

Traceback (most recent call last):
  File "/home/coolduke/.local/bin/memory-channels-processor", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/memory/channels/processor.py", line 641, in main
    processor.process()
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/memory/channels/processor.py", line 267, in process
    data_target.store_data(self, self.args, data)
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/memory/channels/data_targets.py", line 129, in store_data
    prepared_data = self.prepare_data(data, args)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/memory/channels/data_target_chirp.py", line 37, in prepare_data
    data['chirp_name'] = data.apply(self.get_name, args=(args,), axis=1)
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/pandas/core/frame.py", line 9423, in apply
    return op.apply().__finalize__(self, method="apply")
           ^^^^^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/pandas/core/apply.py", line 678, in apply
    return self.apply_standard()
           ^^^^^^^^^^^^^^^^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/pandas/core/apply.py", line 798, in apply_standard
    results, res_index = self.apply_series_generator()
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/pandas/core/apply.py", line 814, in apply_series_generator
    results[i] = self.f(v)
                 ^^^^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/pandas/core/apply.py", line 133, in f
    return func(x, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/coolduke/.local/pipx/venvs/memory-channels/lib/python3.11/site-packages/memory/channels/data_target_chirp.py", line 69, in get_name
    result = row['callsign'].strip("OE")[0:4].ljust(4, ' ') + row['band'][0:1]
             ^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'strip'