emptySet: NOT DEFINED

[kunlinyu]

ogcapi-features/cql2/standard/schema/cql2.bnf

Line 557 in 76debd8

linearRingText = emptySet | "(" point "," point "," point "," point {"," point } ")";

According to the comment in cql2.bnf, this file should pass this validator: https://www.icosaedro.it/bnf_chk/bnf_chk-on-line.html
But if we paste the whole file to bnf_chk-on-line.html, there is one error:

'''bash
emptySet: NOT DEFINED, used 1 times
'''

I think we should just remove the "emptySet |", because the polygonText should have at least one linearRingText.
Am I correct?

[cportele]

Meeting 2025-12-01: @pvretano will check and create a PR, if necessary