[woff2] Reject fonts without `head' table.

Also fix memory deallocation in case of error.

`head' problem reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=17820

* src/sfnt/sfwoff2.c (reconstruct_glyf): Don't use `stream_close'.
Abort if `head_table' is NULL.
Don't free `transformed_buf' in case of error.
(woff2_open_font): Don't set `uncompressed_buf' to NULL.
2 files changed