Export Selection of reaches and wastewater structures fails

[ponceta]

Describe the bug
Export Selection of reaches and wastewater structures fails :

sqlalchemy.exc.ArgumentError: ON clause, typically a SQL expression or ORM relationship attribute expected, got . 
Traceback (most recent call last):
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\teksi_wastewater_plugin.py", line 605, in actionExportClicked
    self.interlisImporterExporter.action_export()
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\gui\interlis_importer_exporter_gui.py", line 149, in action_export
    raise exception
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\gui\interlis_importer_exporter_gui.py", line 119, in action_export
    self.interlis_importer_exporter.interlis_export(
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\interlis_importer_exporter.py", line 198, in interlis_export
    self._export_to_intermediate_schema(
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\interlis_importer_exporter.py", line 366, in _export_to_intermediate_schema
    twwInterlisExporter.tww_export()
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\interlis_model_mapping\interlis_exporter_to_intermediate_schema.py", line 88, in tww_export
    raise exception
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\interlis_model_mapping\interlis_exporter_to_intermediate_schema.py", line 83, in tww_export
    self._export()
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\interlis_model_mapping\interlis_exporter_to_intermediate_schema.py", line 98, in _export
    self._export_sia405_abwasser()
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\interlis_model_mapping\interlis_exporter_to_intermediate_schema.py", line 212, in _export_sia405_abwasser
    self._export_dryweather_downspout()
  File "C:\Users/pulpoar/AppData/Roaming/QGIS/QGIS3\profiles\pulpoar/python/plugins\teksi_wastewater\interlis\interlis_model_mapping\interlis_exporter_to_intermediate_schema.py", line 826, in _export_dryweather_downspout
    query = query.join(
            ^^^^^^^^^^^
  File "", line 2, in join
  File "C:\OSGeo4W\apps\Python312\Lib\site-packages\sqlalchemy\sql\base.py", line 280, in _generative
    x = fn(self, *args, **kw)
        ^^^^^^^^^^^^^^^^^^^^^
  File "", line 2, in join
  File "C:\OSGeo4W\apps\Python312\Lib\site-packages\sqlalchemy\orm\base.py", line 304, in generate
    fn(self, *args, **kw)
  File "C:\OSGeo4W\apps\Python312\Lib\site-packages\sqlalchemy\orm\query.py", line 2429, in join
    onclause_element = coercions.expect(
                       ^^^^^^^^^^^^^^^^^
  File "C:\OSGeo4W\apps\Python312\Lib\site-packages\sqlalchemy\sql\coercions.py", line 396, in expect
    resolved = impl._literal_coercion(
               ^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\OSGeo4W\apps\Python312\Lib\site-packages\sqlalchemy\sql\coercions.py", line 899, in _literal_coercion
    self._raise_for_expected(element)
  File "C:\OSGeo4W\apps\Python312\Lib\site-packages\sqlalchemy\sql\coercions.py", line 518, in _raise_for_expected
    raise exc.ArgumentError(msg, code=code) from err
sqlalchemy.exc.ArgumentError: ON clause, typically a SQL expression or ORM relationship attribute expected, got .

To Reproduce
Export Selection to DSS

1. Select some connected reaches and wastewater structures
2. Click on export
3. Click on limit to selection
4. See error

Expected behavior
A selection can be easily exported

Screenshots / data
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Desktop (please complete the following information):

• QGEP plugin version
• QGEP datamodel version
• QGEP project file version
• QGIS Version
• OS

Additional context
Add any other context about the problem here.

[sjib]

Wrong selection criteria _export_dryweather_downspout