Fix wrong custody column count for lookup blocks (#7281)

Fixes
- https://github.com/sigp/lighthouse/issues/7278


  Don't assume 0 columns for `RpcBlockInner::Block`

beacon_node/network/src/sync/network_context.rs

@@ -1308,7 +1308,7 @@ impl<T: BeaconChainTypes> SyncNetworkContext<T> {
         &self,
         id: Id,
         block_root: Hash256,
-        block: RpcBlock<T::EthSpec>,
+        block: Arc<SignedBeaconBlock<T::EthSpec>>,
         seen_timestamp: Duration,
     ) -> Result<(), SendErrorProcessor> {
         let span = span!(
@@ -1322,6 +1322,12 @@ impl<T: BeaconChainTypes> SyncNetworkContext<T> {
             .beacon_processor_if_enabled()
             .ok_or(SendErrorProcessor::ProcessorNotAvailable)?;
 
+        let block = RpcBlock::new_without_blobs(
+            Some(block_root),
+            block,
+            self.network_globals().custody_columns_count() as usize,
+        );
+
         debug!(block = ?block_root, id, "Sending block for processing");
         // Lookup sync event safety: If `beacon_processor.send_rpc_beacon_block` returns Ok() sync
         // must receive a single `SyncMessage::BlockComponentProcessed` with this process type