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/tests/range.rs

@@ -459,7 +459,8 @@ fn build_rpc_block(
             )
             .unwrap()
         }
-        None => RpcBlock::new_without_blobs(None, block),
+        // Block has no data, expects zero columns
+        None => RpcBlock::new_without_blobs(None, block, 0),
     }
 }