stmgr: More correct fix for genesis state compute

chain/stmgr/execute.go

@@ -52,6 +52,16 @@ func (sm *StateManager) TipSetState(ctx context.Context, ts *types.TipSet) (st c
 
 	sm.stlk.Unlock()
 
+	if ts.Height() == 0 {
+		// NB: This is here because the process that executes blocks requires that the
+		// block miner reference a valid miner in the state tree. Unless we create some
+		// magical genesis miner, this won't work properly, so we short circuit here
+		// This avoids the question of 'who gets paid the genesis block reward'.
+		// This also makes us not attempt to lookup the tipset state with
+		// tryLookupTipsetState, which would cause a very long, very slow walk.
+		return ts.Blocks()[0].ParentStateRoot, ts.Blocks()[0].ParentMessageReceipts, nil
+	}
+
 	st, rec, err = sm.tsExec.ExecuteTipSet(ctx, sm, ts, sm.tsExecMonitor, false)
 	if err != nil {
 		return cid.Undef, cid.Undef, err