ash: fix a memory leak

The script which triggers the leak:

while true
  do
    while true
      do
        break;
    done</dev/null
done

Signed-off-by: Jon Tollefson <kniht@linux.vnet.ibm.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash.c

@@ -8676,6 +8676,8 @@ expredir(union node *n)
 #if ENABLE_ASH_BASH_COMPAT
  store_expfname:
 #endif
+			if (redir->nfile.expfname)
+				stunalloc(redir->nfile.expfname);
 			redir->nfile.expfname = fn.list->text;
 			break;
 		case NFROMFD: