Not All ReadSkeletonHeader check the return value equals nil

[lyciumlee]

System information

Geth version: geth version v1.12.2
CL client & version: e.g. lighthouse/nimbus/prysm@v1.0.0
OS & Version: Windows/Linux/OSX
Commit hash : (if develop)

Expected behaviour

ret := rawdb.ReadSkeletonHeader(x,xx)
we should check if ret == nil

Actual behaviour

	if lastchain.Tail >= number {
		// If the chain is down to a single beacon header, and it is re-announced
		// once more, ignore it instead of tearing down sync for a noop.
		if lastchain.Head == lastchain.Tail {
			if current := rawdb.ReadSkeletonHeader(s.db, number); current.Hash() == head.Hash() {
				return false
			}

if parent := rawdb.ReadSkeletonHeader(s.db, number-1); parent.Hash() != head.ParentHash {
	if force {
		log.Warn("Beacon chain forked", "ancestor", parent.Number, "hash", parent.Hash(), "want", head.ParentHash)
	}
	return true
}

Steps to reproduce the behaviour

Backtrace

[backtrace]

we should check the return value.