dtprintinfo: Fix SIGSEGV in dtprintinfo (passing NULL as first argument to catgets).

dtprintinfo: Fix SIGSEGV in dtprintinfo (passing NULL as first argument to catgets).

Patch from Douglas Mencken <dougmencken@gmail.com>:

The issue is that MESSAGE tries to invoke catgets with NULL first
parameter, which is dereferenced inside catgets (Std C Library
function) without checking, from catgets.c source:

if (catalog->name_ptr[idx + 0] == (u_int32_t) set
          && catalog->name_ptr[idx + 1] == (u_int32_t) message)

On the other hand, there's a special value: -1 (cast to nl_catd),
which must be used instead of 0 (NULL) in the case when we are unable
to provide real catalog_desc, from catgets.c source:

  /* Be generous if catalog which failed to be open is used.  */
  if (catalog_desc == (nl_catd) -1 || ++set <= 0 || message < 0)
    return (char *) string;