Is hex 00000 in a string field equal to null?

I have been trying to figure out this bug in my .NET program for the last
couple months. For background, it is for signing time sheets. The .NET
program calls a stored procedure that executes a RPG program that marks the
time sheet as signed. Occasionally, something happens (a couple times per
cycle for about 100 employees or so) that causes my program to crash
(please avoid the .NET jokes here). I might be able to handle the bug okay
now that I know what to expect, but I am trying to determine what that data
is and why it is in there.

I ran the following statement:

SELECT EM_FULL_N, HEX(EMP_COMMENTS), HEX(SUPV_COMMENTS) FROM MPRTCSP
WHERE EMP_COMMENTS <> '' OR SUPV_COMMENTS <> ''

and got the following result (edited for length):

HEX
HEX
4040404040404040404040404040404040404040...40
00000000000000000000000000000000000000000....00

I know x40 is blanks but what is x00. Is that null?

--
Mike Wills
http://mikewills.me