postgresql v6.4.2 c funcs and null text pointers...

I wrote a c func (ATTACHED BELOW) which takes 2 pointers to type text, and
a bool field.  When a field in a row passed to the func is null, espically
the 'first' field, Postgresql does not return the value that my code
produced.

For example:  
First		lastco		nocompany
------------------------------------------
NULL            Walt Bigelow    True

the above data is contained in the database, and when passed to my c func
like:

SELECT lastfirst(first, lastco, nocompany) as name from tbladdress where
agencyid = 691;

I get:
name
----

(1 row)

Not the expected output of 'Walt Bigelow, '.

When I update that row with first = '', the result is correct, but the
value is no null, so it works.

What am I missing??

Any help is appricated,
Walt

-------------
name.c:

#include <string.h>
#include "postgres.h"

#define		COMMA	", "

text *lastfirst (text *first, text *last, bool nocompany)
{
/* this function will take in the first name, and last name
 * and based on nocompany set the output to either return 
 * 'last, first' or just the company name.
 */

int32	ret_size;
text	*return_text;

	if (nocompany) {
		
		if (first == NULL) {
			
			ret_size = VARSIZE(last) + sizeof(COMMA);
			return_text = (text *) palloc(ret_size);

			memset(return_text, 0, ret_size);

			VARSIZE(return_text) = ret_size;

			strncpy (VARDATA(return_text), VARDATA(last), 
				VARSIZE(last)-VARHDRSZ);
			
			strncat (VARDATA(return_text), COMMA,
				sizeof(COMMA));

			return (return_text);
		
		} else {
		
			ret_size = VARSIZE(first) + VARSIZE(last) + 
				sizeof(COMMA) - VARHDRSZ;
		
			return_text = (text *) palloc(ret_size);

			memset(return_text, 0, ret_size);

			VARSIZE(return_text) = ret_size;

			strncpy (VARDATA(return_text), VARDATA(last), VARSIZE(last)-VARHDRSZ);
			strncat (VARDATA(return_text), COMMA, sizeof(COMMA));
			strncat (VARDATA(return_text), VARDATA(first), VARSIZE(first)-VARHDRSZ);

			return (return_text);

		}

	} else {
		/* Just the company name is returned here */

		ret_size = VARSIZE(last);
		return_text = (text *) palloc(ret_size);
				
		VARSIZE(return_text) = ret_size;
		strncpy(VARDATA(return_text), VARDATA(last),
			VARSIZE(last)-VARHDRSZ);
				
		return (return_text);
	}
}