revlog: remove micro-optimization for looking up only nullid index_find_node() would call nt_find() before initializing the node tree. nt_find() would then return -2 unless the requested revision was the null revision. I can't imagine what scenario that is optimizing for, and doing the initialization earlier makes the code simpler and easier to follow, so that's what this patch does. Differential Revision: https://phab.mercurial-scm.org/D4027