[truetype] Add better checks for loading `gvar' table (#57905).

* src/truetype/ttgxvar.c (ft_var_load_gvar): Delay settings of any
`blend->xxxcount' values until the corresponding data has been
checked.
Also do some sanitizing to avoid a too early exit.

(TT_Vary_Apply_Glyph_Deltas): Improve tracing message.
2 files changed