Best known invalid block, tracked to detect a longer invalid chain than the valid one.
Declared in <validation.h>
[[guarded_by(0x7fbc8fcf84f8), guarded_by(0x7fbc96d90cb8), guarded_by(0x7fbcaf726728), guarded_by(0x7fbc9e23de08)]]
CBlockIndex* m_best_invalid = {nullptr};