adm_config_report: improve invalid config handling

When receiving an invalid config_id, the page will default the select to
[any] (META_FILTER_NONE) instead of adding the invalid config to the
list.

Improvement over cabacdc291c251bfde0dc2a2c945c02cef41bf40, we don't
really need to trigger an error here, it's more user-friendly to fall
back to a sensible default, similar to what we do when given an invalid
project.