ftplib::FtpClose - please add NULL pointer checking, otherwise unwanted crash may occur.

[Fojtik]

When NULL is not checked, passing NULL pointer causes crash when attempting to dereference nData->dir. As far as int FtpClose(ftphandle *nData); is not internal function, the argument passed cannot be guaranteed.

/*
 * FtpClose - close a data connection
 */
int ftplib::FtpClose(ftphandle *nData)
{
	ftphandle *ctrl;

	if (nData->dir == FTPLIB_WRITE)
	{
		if (nData->buf != NULL) writeline(NULL, 0, nData);
	}
	else if (nData->dir != FTPLIB_READ) return 0;
	if (nData->buf) free(nData->buf);
	shutdown(nData->handle,2);
	net_close(nData->handle);

Please add NULL pointer checking here:

/*
 * FtpClose - close a data connection
 */
int ftplib::FtpClose(ftphandle *nData)
{
  ftphandle *ctrl;

  if (nData==NULL) return 0;
  if (nData->dir == FTPLIB_WRITE)
  {
    if (nData->buf != NULL) writeline(NULL, 0, nData);
  }