Gjallarhorn: Render pool should ignore playback segments which are empty.

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/state/BlockMapRenderPool.kt

@@ -59,6 +59,9 @@ class BlockMapRenderPool<T>(
     val sliced = changelog.slice(slice)
     val tracker = BlockLogTracker(blockTrackMode)
     tracker.replay(sliced)
+    if (tracker.isEmpty()) {
+      return
+    }
     trackers[slice] = tracker
   }