Request failed when user try apply "Not specified" filter on the "Accession browser" page

Steps to reproduce:

1. Open "https://sandbox.genesys-pgr.org/a/overview"
2. Apply "Not specified" filter from "Genus" block

Expected result: Filter is applied and results are shown

Actual result:

Error happened while processing request:

"Request failed with status code 500 Error accessing field taxonomy.genus for isNull() in class org.genesys2.server.model.genesys.QAccession"

This bug reproduce with "Genys", "Type of Germplasm storage" and "Provenance of material" blocks