Do oracle objects have two types of NULL?

 I' m looking for an explanation for that case:

I create an object type an its related collection type.

If I create a NULL row with a constructor I can't compare it with a NULL row create with extend method.

Have a look at the example code:

DROP TYPE ORATEST_TYPE_EMAIL_TABLE;

DROP TYPE ORATEST_TYPE_EMAIL;

CREATE OR REPLACE TYPE "ORATEST_TYPE_EMAIL" AS OBJECT

(

   OI_LINE_ID NUMBER (15),

   OI_OFF_ID NUMBER (20),

   OI_CHANGING_DATE DATE,

   OI_EMAIL_STRING VARCHAR2 (254),

   MAP MEMBER FUNCTION MAPPER

      RETURN VARCHAR2,

     CONSTRUCTOR FUNCTION ORATEST_TYPE_EMAIL

      RETURN SELF AS RESULT   

);

/

CREATE OR REPLACE TYPE BODY ORATEST_TYPE_EMAIL