bssnEScalar_class::Initialize() already calls setup_transfer_caches(),
but bssnEM_class::Initialize() did not. When USE_TRANSFER_CACHE=1,
the sync_cache pointers remain NULL, causing SIGSEGV in wrapper
methods that dereference sync_cache_*[lev].
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
