another ecpg crash

Hi,

I found another bug when using 'exec sql include filename'. If you use a
filename that doesn't exist, ecpg crashes while trying to close a null
pointer. The above test case shows it. A possible fix is attached.

#include <stdio.h>

/* foo.h doesn't exist */
exec sql include foo;

int main(void)
{
    return 0;
}


(gdb) bt
#0  0xb7a746fd in fclose@@GLIBC_2.1 () from /lib/libc.so.6
#1  0x080496e1 in mmerror (error_code=2, type=ET_FATAL, error=0xb7eeb0cc
<Address 0xb7eeb0cc out of bounds>)
     at /a/pgsql/dev/pgsql/src/interfaces/ecpg/preproc/preproc.y:93
#2  0x08069d07 in parse_include () at
/a/pgsql/dev/pgsql/src/interfaces/ecpg/preproc/pgc.l:1270
#3  0x08067fa7 in base_yylex () at
/a/pgsql/dev/pgsql/src/interfaces/ecpg/preproc/pgc.l:1080
#4  0x0806d4ce in filtered_base_yylex () at
/a/pgsql/dev/pgsql/src/interfaces/ecpg/preproc/parser.c:64
#5  0x0804a8a8 in base_yyparse () at y.tab.c:20322
#6  0x0806ca35 in main (argc=2, argv=0xbff0ea94) at
/a/pgsql/dev/pgsql/src/interfaces/ecpg/preproc/ecpg.c:462
(gdb) print yyin
$1 = (FILE *) 0x0


--
   Euler Taveira de Oliveira
   http://www.timbira.com/
*** ./src/interfaces/ecpg/preproc/preproc.y.orig    2008-05-11 01:28:52.000000000 -0300
--- ./src/interfaces/ecpg/preproc/preproc.y    2008-05-11 01:43:24.000000000 -0300
***************
*** 90,96 ****
              ret_value = error_code;
              break;
          case ET_FATAL:
!             fclose(yyin);
              fclose(yyout);
              if (unlink(output_filename) != 0 && *output_filename != '-')
                      fprintf(stderr, _("could not remove output file \"%s\"\n"), output_filename);
--- 90,98 ----
              ret_value = error_code;
              break;
          case ET_FATAL:
!             /* there are some cases (i.e. file not found) that the input is not available */
!             if (!yyin)
!                 fclose(yyin);
              fclose(yyout);
              if (unlink(output_filename) != 0 && *output_filename != '-')
                      fprintf(stderr, _("could not remove output file \"%s\"\n"), output_filename);