Update BlockFetcherState with suggestion from review

Co-authored-by: Anastasiia Pushkina <[email protected]>

Author: bsuieric

src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockFetcherState.scala

@@ -129,11 +129,11 @@ case class BlockFetcherState(
         )
     }
 
-  private def checkConsistencyWithReadyBlocks(headers: Seq[BlockHeader]): Boolean = {
-    if (waitingHeaders.isEmpty) {
-      (readyBlocks.lastOption.map(_.header), headers.headOption).mapN(_ isParentOf _).getOrElse(true)
-    } else true
-  }
+ private def checkConsistencyWithReadyBlocks(headers: Seq[BlockHeader]): Boolean = {
+    (readyBlocks, headers) match {
+      case (_ :+ last, head +: _) if waitingHeaders.isEmpty  => last.header isParentOf head
+      case _ => true
+    }
 
   def validateNewBlockHashes(hashes: Seq[BlockHash]): Either[String, Seq[BlockHash]] =
     hashes