fix: Find index with empty string.

[EdwinBetanc0urt]

When searching with an empty text in a parameter, it is considered as part of the index because it is not null, so it is not marked as an empty mandatory.

[yamelsenih]

Hey, just validate this and is ok: https://github.com/adempiere/dictionary_rs/blob/main/src/bin/server.rs#L333

[EdwinBetanc0urt]

@yamelsenih It is validated if the variable is not null but not if it has an empty string, if you send language= it will not say that it is mandatory and considers it a valid value.