fix crash in block entity ticker, fix wrong displayed available audio source number in f3

src/main/java/de/bixilon/minosoft/data/world/ChunkSection.kt

@@ -58,7 +58,8 @@ class ChunkSection(
 
     fun realTick(connection: PlayConnection, chunkSectionPosition: Vec3i) {
         blockEntities.forEach { entity, inChunkSectionPosition ->
-            entity.realTick(connection, blocks[inChunkSectionPosition.index]!!, chunkSectionPosition + inChunkSectionPosition)
+            val block = blocks[inChunkSectionPosition.index] ?: return@forEach // maybe block already got destroyed
+            entity.realTick(connection, block, chunkSectionPosition + inChunkSectionPosition)
         }
     }
 

src/main/java/de/bixilon/minosoft/gui/rendering/sound/AudioPlayer.kt

@@ -67,19 +67,9 @@ class AudioPlayer(
     private lateinit var listener: SoundListener
     private val sources: MutableList<SoundSource> = synchronizedListOf()
 
-    val availableSources: Int
+    var availableSources: Int = 0
-        get() {
+        private set
-            val sources = sources.toSynchronizedList()
-            var available = 0
 
-            for (source in sources) {
-                if (source.available) {
-                    available++
-                }
-            }
-
-            return available
-        }
     val sourcesCount: Int
         get() = sources.size
 
@@ -207,6 +197,15 @@ class AudioPlayer(
                 break
             }
             queue.work()
+
+            var availableSources = 0
+            for (source in sources) {
+                if (source.available) {
+                    availableSources++
+                }
+            }
+            this.availableSources = availableSources
+
             Thread.sleep(1L)
         }
     }

src/main/java/de/bixilon/minosoft/gui/rendering/sound/SoundSource.kt

@@ -73,7 +73,7 @@ class SoundSource {
         get() = alGetSourcei(source, AL_SOURCE_STATE) == AL_PLAYING
 
     val available: Boolean
-        get() = !isPlaying || System.currentTimeMillis() - playTime > (sound?.length ?: 0L) // ToDo: Allow pause
+        get() = !isPlaying || System.currentTimeMillis() - playTime > (sound?.length ?: 0L)    // ToDo: Allow pause
 
     fun play() {
         playTime = System.currentTimeMillis()