core/types: add length check in CalcRequestsHash

The existing implementation is correct when building and verifying blocks, since we will
only collect non-empty requests into the block requests list.

But it isn't correct for cases where a requests list containing empty items is sent by the
consensus layer on the engine API. We want to ensure that empty requests do not cause a
difference in validation there, so the commitment computation should explicitly skip them.

core/types/block.go

@@ -463,10 +463,12 @@ func CalcRequestsHash(requests [][]byte) common.Hash {
 	h1, h2 := sha256.New(), sha256.New()
 	var buf common.Hash
 	for _, item := range requests {
+		if len(item) > 1 { // skip items with only requestType and no data.
 			h1.Reset()
 			h1.Write(item)
 			h2.Write(h1.Sum(buf[:0]))
 		}
+	}
 	h2.Sum(buf[:0])
 	return buf
 }