[truetype] Better protection against invalid VF data. Reported as https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=5739 Bug introduced in commit 08cd62deedefe217f2ea50e392923ce8b5bc7ac7. * src/truetype/ttgxvar.c (TT_Set_Var_Design): Always initialize `normalizedcoords'.