If party is NULL, print: -> Bloop! NULL pointer detected in delete(). Returns: Return LPA_FAILURE if this operation refers to an invalid index (as defined in the set() function description), if this function receives a NULL party pointer, if this operation refers to a cell that lies within an unallocated fragment, or if this operation refers to a cell whose value was already set to UNUSED when the function was called. Otherwise, return LPA_SUCCESS.