Allow empty sparse matrix inputs to qr() (bug #63069) * qr.cc (Fqr): Add BIST tests for bug #63069. * sparse-qr.cc (sparse_qr<SparseMatrix>::sparse_qr_rep::sparse_qr_rep, sparse_qr<SparseMatrix>::sparse_qr_rep::C, sparse_qr<SparseMatrix>::sparse_qr_rep::tall_solve<MArray<double>, Matrix>, sparse_qr<SparseComplexMatrix>::sparse_qr_rep::sparse_qr_rep, sparse_qr<SparseComplexMatrix>::sparse_qr_rep::C, sparse_qr<SPARSE_T>::solve): Change input validation from "<= 0" to "< 0". Change error message to "matrix dimension with negative size" from "matrix dimension with negative or zero size".

%!function rval = sggval (val)
%!  global gval
%!  if (nargin == 1)
%!    gval = val;
%!  else
%!    rval = gval;
%!  endif
%!endfunction

%!test <*53599>
%! global gval
%! assert (isempty (gval))
%! sggval (13);
%! assert (sggval (), 13);
%! assert (gval, 13);
%! clear global gval
%! assert (sggval (), [])
%! gval = 42;
%! assert (sggval (), []);
%! clear gval
%! global gval
%! gval = 42;
%! assert (sggval (), 42);
%! clear -global gval;  # cleanup after test