[pshinter] Fully initialize globals->blues.
These defaults may be overriden later by `psh_blues_scale_zones` which is conditionally called from `psh_globals_set_scale`. * src/pshinter/pshglob.c (psh_globals_new): initialize `blues->blue_threshold` and `blues->no_overshoots`. Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=43701