Lifetime of PQexecPrepared() returned value

Hi, ALL,
I have a following piece of code:

[code]
PGresult *res = PQexecPrepared();
status = PQresultStatue( res );
if( status == PGRES_TUPLES_OK )
{
for( int j = 0; j < PQntuples( res ); j++ )
{
char *foo = PQgetValue( res, j, 0 );
char *bar = PQgetValue( res, j, 1 );
MyObject *obj = new MyObject( foo, bar );
if( SetAdditionalProperties( obj ) )
{
result = 1;
break;
}
}
PQclear( res );
}

int SetAdditionalProperties(MyObject &obj)
{
// a call to PQexecParams() here
}
[/code]

If the call to SetAdditionalProperties() fails, I get a crash on
PQclear(), stating that
the pointer is not allocated.

Am I missing something? How do I fix the crash?

Thank you.