Prevent null exceptions. Check if no more blocks.

src/main/java/dev/zontreck/libzontreck/memory/world/BlockRestoreRunner.java

@@ -26,6 +26,7 @@ public class BlockRestoreRunner implements Runnable
         if(queue.getQueuedBlocks() == 0 && !queue.usesDatabase()) return; // We'll be queued back up later
 
         PrimitiveBlock prim = queue.getNextBlock();
+        if(prim == null)return; // No more blocks.
 
         Level level = prim.level;