Script 'global_descriptive_statistics.py' shows an error due to an array length mismatch

The following Trace shows that there is an array length mismatch in script 'global_descriptive_statistics.py':

Generating descriptive statistics
Traceback (most recent call last):
  File "/usr/local/bin/survey_analysis", line 33, in <module>
    sys.exit(load_entry_point('SurveyAnalysis2020', 'console_scripts', 'survey_analysis')())
  File "/home/christianhueser/.local/lib/python3.8/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/home/christianhueser/.local/lib/python3.8/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/home/christianhueser/.local/lib/python3.8/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/christianhueser/.local/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/christianhueser/.local/lib/python3.8/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/home/christianhueser/git_repositories/hifis_software_survey_2019_2020/survey-analysis-framework-20210224/survey_analysis/cli.py", line 142, in analyze
    dispatcher.load_all_modules()
  File "/home/christianhueser/git_repositories/hifis_software_survey_2019_2020/survey-analysis-framework-20210224/survey_analysis/dispatch.py", line 86, in load_all_modules
    self.load_module(module_name)
  File "/home/christianhueser/git_repositories/hifis_software_survey_2019_2020/survey-analysis-framework-20210224/survey_analysis/dispatch.py", line 111, in load_module
    module.run()
  File "/home/christianhueser/git_repositories/hifis_software_survey_2019_2020/survey-analysis-framework-20210224/scripts/global_descriptive_statistics.py", line 139, in run
    question_data_grouped_relative = question_data_grouped_relative.set_index(
  File "/home/christianhueser/.local/lib/python3.8/site-packages/pandas/core/frame.py", line 4588, in set_index
    raise ValueError(
ValueError: Length mismatch: Expected 19 rows, received array of length 18

Some debugging shows that when long center names are mapped to short center names the mapping for "None => No center affiliation" is missing.