Null row is occurring in OTBI because of Case statement

I am facing some strange issue where null row is getting when i had use case statement one of the attribute as we have multiple phone types and for one of the employee having two MFA Phone numbers but unfortunately OTBI Result is printing with three rows as third row as Null when i use case statement.

I am using Workforce Management -Person Ream Time Subject Area

Our Expected Result should be two rows as i am not sure why null row is coming

Cast Statement: CASE WHEN "Person Phones"."Phone Type Code" = 'MFA_PHONE' Then "Person Phones"."Search Phone Number"  End