Fix walking main branch of forkdb
When we are switching to a fork, this function would report a block as on the main branch after it had been popped and before it had been re-pushed.
Made minor optimization while walking main branch in forkdb.
When we are switching to a fork, this function would report a block as on the main branch after it had been popped and before it had been re-pushed.
Made minor optimization while walking main branch in forkdb.