How to check if a google sheet cell is empty if it has data validation set on date input?

Question

Google

The problem is next. The table has two columns. Column A is filled in automatically after column B is filled with the date. At the same time, column B has a data check for entering a date. Condition for column A: =IF((MONTH(B4))=1;"January",(IF((MONTH(B4))=2;"February";( IF((MONTH(B4))=3;" March";(IF((MONTH(B4))=4;"April";( IF((MONTH(B4))=5;"May";(IF((MONTH(B4))=6;"June" ;( IF((MONTH(B4))=7;"July";(IF((MONTH(B4))=8;"August";(IF((MONTH(B4))=9;"September";( IF((MONTH(B4))=10;"October";( IF((MONTH(B4))=11;"November";(IF((MONTH(B4))=12;"December";"Date not selected"))))))))))))))))))))))))) The
problem is in the last condition.date is selected, then everything works, otherwise the value "December" is still returned...