Excel export fail

[sixy6e]

QAX fails to export the results of a density check to Excel.

[sixy6e]

Traceback:

 ERROR     root.export_qajson_excel:184 > Traceback (most recent call last):
  File "hyo2\qax\lib\project.py", line 177, in export_qajson_excel
    exporter.export(
  File "hyo2\qax\lib\qajson_util.py", line 395, in export
    tableSummary.build()
  File "hyo2\qax\lib\qajson_util.py", line 266, in build
    value = self._get_field_value(field.name, section.name, filename)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "hyo2\qax\lib\qajson_util.py", line 254, in _get_field_value
    value = plugin.get_summary_value(section_name, field_name, filename, self.qajson)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "ausseabed\mbesgc\qax\plugin.py", line 253, in get_summary_value
AttributeError: 'NoneType' object has no attribute 'outputs'

[sixy6e]

Resolved by ausseabed/mbes-grid-checks#4