updatelayer raises exception on tabular data

[ridoo]

updatelayers command raises on datasets which have subtype=tabular:

root@2fdce1e77dc2:/usr/src/geonode# python manage.py updatelayers
Inspecting the available layers in GeoServer ...
Found 2 layers, starting processing
WARNING Could not clean style for layer horizon_data
Traceback (most recent call last):
  File "/usr/src/geonode/geonode/geoserver/helpers.py", line 1130, in clean_styles
    logger.debug(f'clean_styles: Retrieving style "{gs_dataset.default_style.name}" for cleanup')
AttributeError: 'NoneType' object has no attribute 'name'

[ridoo]

After fixing some other issues, now I get (could be related to #18):

ERROR java.lang.NullPointerException
Traceback (most recent call last):
  File "/usr/src/geonode/geonode/thumbs/utils.py", line 219, in get_map
    image = getmap(
  File "/usr/src/geonode/geonode/thumbs/utils.py", line 436, in getmap
    raise ServiceException(err_message)
owslib.util.ServiceException: java.lang.NullPointerException
ERROR java.lang.NullPointerException
Traceback (most recent call last):
  File "/usr/src/geonode/geonode/thumbs/utils.py", line 219, in get_map
    image = getmap(
  File "/usr/src/geonode/geonode/thumbs/utils.py", line 436, in getmap
    raise ServiceException(err_message)
owslib.util.ServiceException: java.lang.NullPointerException

Corresponding GeoServer logs:

geoserver4geonode_datapackage  | java.lang.NullPointerException
geoserver4geonode_datapackage  |        at org.geoserver.wms.map.GetMapKvpRequestReader.getDefaultStyle(GetMapKvpRequestReader.java:1044)
geoserver4geonode_datapackage  |        at org.geoserver.wms.map.GetMapKvpRequestReader.processLayersStyles(GetMapKvpRequestReader.java:655)
geoserver4geonode_datapackage  |        at org.geoserver.wms.map.GetMapKvpRequestReader.read(GetMapKvpRequestReader.java:460)
geoserver4geonode_datapackage  |        at org.geoserver.wms.map.GetMapKvpRequestReader.read(GetMapKvpRequestReader.java:107)
geoserver4geonode_datapackage  |        at org.geoserver.ows.Dispatcher.parseRequestKVP(Dispatcher.java:1509)
geoserver4geonode_datapackage  |        at org.geoserver.ows.Dispatcher.dispatch(Dispatcher.java:682)
geoserver4geonode_datapackage  |        at org.geoserver.ows.Dispatcher.handleRequestInternal(Dispatcher.java:258)
geoserver4geonode_datapackage  |        at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:177)
geoserver4geonode_datapackage  |        at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:51)

[ridoo]

We should consider to configure THUMBNAIL_GENERATOR with a custom implementation to handle the tabular case. Do this in one go with GeoNodeUserGroup-DE/contrib_datapackage#12.