This function sets an SbData structure to hold the undefined value.
This function should should not be used instead of scriba_InitSbData(). While that function should be used to inititalize the memory structure this function should be used to set the value of an alreasdy initialized and probably used SbData variable to undef.
The difference inside is that if the SbData structure is a string then this function releases the memory occupied by the string, while scriba_InitSbData() does not.
See also scriba_NewSbLong(), scriba_NewSbDouble(), scriba_NewSbUndef(), scriba_NewSbString(), scriba_NewSbBytes(), scriba_DestroySbData().
void scriba_UndefSbData(pSbProgram pProgram,