Issue with passing NULL for function parameter

I have wriiten following simple function in postgresql

CREATE OR REPLACE FUNCTION "MySchema".add_user(p_name character varying, p_=
email1 character varying, p_email2 character varying)
  RETURNS bigint AS
$BODY$
DECLARE
                userId bigint;
BEGIN
                INSERT INTO "MySchema"."User"("Name" ,"EMail1" , "EMail2")
                                VALUES ($1 , $2, $3) ;

                Select CURRVAL('"MySchema".user_seq_userid') into userId;

                return userid;
END;
$BODY$
  LANGUAGE plpgsql VOLATILE STRICT

Function works absoolutely fine if I provide values for all three parameter=
s. Record gets inserted too.

But if I pass NULL for say last parameter, using  SELECT "MySchema".add_use=
r('A' , 'A', NULL)
function does not do anything and return zero.
No error is shown. But record is not inserted in table.
All columns in table can have NULL value.

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