Miner: Don't request deal weight for empty deal array

[wadealexc]

Miner.PreCommitSector makes an unnecessary call to the Market actor when precommitting a CC Sector:

specs-actors/actors/builtin/miner/miner_actor.go

Lines 1933 to 1944 in 9d42fb1

	func requestDealWeight(rt Runtime, dealIDs []abi.DealID, sectorStart, sectorExpiry abi.ChainEpoch) market.VerifyDealsForActivationReturn {
	var dealWeights market.VerifyDealsForActivationReturn
	ret, code := rt.Send(
	builtin.StorageMarketActorAddr,
	builtin.MethodsMarket.VerifyDealsForActivation,
	&market.VerifyDealsForActivationParams{
	DealIDs: dealIDs,
	SectorStart: sectorStart,
	SectorExpiry: sectorExpiry,
	},
	abi.NewTokenAmount(0),
	)

Recommendation

requestDealWeight should not invoke the market actor if len(dealIDs) == 0

[anorth]

Closing as duplicate of #474, even though it's only part of it.