[sfnt] Fix off-by-one error.

The 0-base index is equal to the number of previosly parsed entries.
It is an error to adjust it by one to get the number truncated by
a stream error.  This is probably inconsequential because valid
entries are correctly accounted for.

* src/sfnt/ttload.c (check_table_dir): Do not adjust the truncated
number of tables.
diff --git a/src/sfnt/ttload.c b/src/sfnt/ttload.c
index 51416d8..97e47f8 100644
--- a/src/sfnt/ttload.c
+++ b/src/sfnt/ttload.c
@@ -205,7 +205,6 @@
       if ( FT_STREAM_READ_FIELDS( table_dir_entry_fields, &table ) )
-        nn--;
         FT_TRACE2(( "check_table_dir:"
                     " can read only %d table%s in font (instead of %d)\n",
                     nn, nn == 1 ? "" : "s", sfnt->num_tables ));