Add CASE_WHEN_THEN_ELSE construction support with FireBird

[umkaline]

Currently Component fails on select trigger with the following query:

select distinct  
				MATERIALCODE
				,locationid
				,CASE WHEN m.DELIVERYBLOCK= 0 THEN 1 ELSE 0 END AS Active
				,COUNRTYORIGINID
				,ALTERNATIVESUPPLIERNUM
				,MINQTY
				,CASE WHEN DEFAULTPARTNERNUM=ALTERNATIVESUPPLIERNUM THEN 1 ELSE MINQTY END AS USQ
				,AVGDELIVERYPRICE
				,MATERIALALTERNATIVENAME
				,LASTEDITUSERID
				,EXPIRATIONDATE
			from MATERIAL m
			where LOCATIONID = 2

With an error:
java.sql.SQLException: Empty string does not identify column.

Issue disappearing if Case is removed.