* src/files.c (write_file): Check stat struct exists, and if not use just obtained stat data.    
          Fixes Ubuntu bug 471568, "reproducible crash in nano on trying to save to a file 
          different than the one specified on the command line".



git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@4467 35c25a1d-7b9e-4130-9fde-d3aeb78583b8