Fixes #452

- ChunkSections containing only air are technically null according to NMS Chunks
- Therefore if we're replacing air, we should ignore the result of get.hasSection(layer) by using "full = true" as it returns false if the chunksection is only air
- We also then need to ensure that the masks correctly identify that the block is "air"

worldedit-core/src/main/java/com/boydti/fawe/beta/implementation/queue/ParallelQueueExtent.java

@@ -162,7 +162,8 @@ public class ParallelQueueExtent extends PassthroughExtent implements IQueueWrap
     @Override
     public int replaceBlocks(Region region, Mask mask, Pattern pattern)
         throws MaxChangedBlocksException {
-        return this.changes = apply(region, mask.toFilter(pattern), false).getBlocksApplied();
+        boolean full = mask.replacesAir();
+        return this.changes = apply(region, mask.toFilter(pattern), full).getBlocksApplied();
     }
 
     @Override