fix: handle negative slots in SyncBlocks

Author: MegaRedHand

lib/lambda_ethereum_consensus/beacon/sync_blocks.ex

@@ -29,16 +29,18 @@ defmodule LambdaEthereumConsensus.Beacon.SyncBlocks do
     initial_slot = Misc.compute_start_slot_at_epoch(checkpoint.epoch) + 1
     last_slot = BeaconChain.get_current_slot()
 
-    chunks =
-      Enum.chunk_every(initial_slot..last_slot, @blocks_per_chunk)
-      |> Enum.map(fn chunk ->
-        first_slot = List.first(chunk)
-        last_slot = List.last(chunk)
-        count = last_slot - first_slot + 1
-        %{from: first_slot, count: count}
-      end)
-
-    perform_sync(chunks)
+    if last_slot > 0 do
+      chunks =
+        Enum.chunk_every(initial_slot..last_slot, @blocks_per_chunk)
+        |> Enum.map(fn chunk ->
+          first_slot = List.first(chunk)
+          last_slot = List.last(chunk)
+          count = last_slot - first_slot + 1
+          %{from: first_slot, count: count}
+        end)
+
+      perform_sync(chunks)
+    end
   end
 
   @spec perform_sync([chunk()]) :: :ok