Heimdall: Fix bug where DB being disabled might cause errors.

foundation-heimdall/src/main/kotlin/cloud/kubelet/foundation/heimdall/FoundationHeimdallPlugin.kt

@@ -29,7 +29,7 @@ import kotlin.io.path.inputStream
 class FoundationHeimdallPlugin : JavaPlugin(), Listener {
   private lateinit var config: HeimdallConfig
   private lateinit var pool: HikariDataSource
-  internal lateinit var db: Database
+  internal var db: Database? = null
 
   private val buffer = EventBuffer()
   private val bufferFlushThread = BufferFlushThread(this, buffer)

foundation-heimdall/src/main/kotlin/cloud/kubelet/foundation/heimdall/buffer/BufferFlushThread.kt

@@ -31,6 +31,11 @@ class BufferFlushThread(val plugin: FoundationHeimdallPlugin, val buffer: EventB
 
   fun flush() {
     try {
+      val db = plugin.db
+      if (db == null) {
+        buffer.clear()
+        return
+      }
       transaction(plugin.db) {
         val count = buffer.flush(this)
         if (count > 0) {

foundation-heimdall/src/main/kotlin/cloud/kubelet/foundation/heimdall/buffer/EventBuffer.kt

@@ -21,4 +21,8 @@ class EventBuffer {
   fun push(event: HeimdallEvent) {
     events.add(event)
   }
+
+  fun clear() {
+    events = mutableListOf()
+  }
 }

tool-gjallarhorn/src/main/kotlin/cloud/kubelet/foundation/gjallarhorn/export/CombinedChunkFormat.kt

@@ -2,8 +2,9 @@ package cloud.kubelet.foundation.gjallarhorn.export
 
 import cloud.kubelet.foundation.gjallarhorn.state.BlockExpanse
 import cloud.kubelet.foundation.gjallarhorn.state.SparseBlockStateMap
+import kotlinx.serialization.Serializable
 
-@kotlinx.serialization.Serializable
+@Serializable
 class CombinedChunkFormat(
   val expanse: BlockExpanse,
   val map: SparseBlockStateMap