Python error when the service return http error 204

When a fdsn (event, macroseismic o station) service returns an https error code 204 "no content", qquake generate a python error.

To reproduce the issue:

select "earthquake parameters"
select "INGV ISIDe"
enter 6 as the minimum magnitude
do not enter any time coverage filter
selecte "Italy" as the predefined geographical coverage filter
select "basic" as the output table format

Below the stack trace of the generated by the Python error

IndexError: list index out of range 
Traceback (most recent call last):
  File "/home/mario/.local/share/QGIS/QGIS3/profiles/default/python/plugins/qquake/gui/qquake_dialog.py", line 966, in _fetcher_finished
    layer = self.fetcher.create_event_layer()
  File "/home/mario/.local/share/QGIS/QGIS3/profiles/default/python/plugins/qquake/fetcher.py", line 774, in create_event_layer
    return self.events_to_layer(self.result, self.preferred_origins_only, self.preferred_magnitudes_only)
  File "/home/mario/.local/share/QGIS/QGIS3/profiles/default/python/plugins/qquake/fetcher.py", line 618, in events_to_layer
    vl = self._create_empty_event_layer()
  File "/home/mario/.local/share/QGIS/QGIS3/profiles/default/python/plugins/qquake/fetcher.py", line 569, in _create_empty_event_layer
    vl.dataProvider().addAttributes(self.result.to_event_fields(self.output_fields))
  File "/home/mario/.local/share/QGIS/QGIS3/profiles/default/python/plugins/qquake/basic_text/basic_text_parser.py", line 186, in to_event_fields
    fields.append(QgsField(self.headers[0], QVariant.String))
IndexError: list index out of range

See the screenshot below

INGV / qquake

Python error when the service return http error 204 #73