Fix //none removing arbitrary nbt

worldedit-core/src/main/java/com/boydti/fawe/util/BrushCache.java

@@ -77,8 +77,11 @@ public final class BrushCache {
         Map<String, Tag> map;
         if (nbt == null) {
             if (tool == null) {
+                Map<String, Object> raw = nbt.getRaw();
+                if (raw.remove("weBrushJson") != null && raw.isEmpty()) {
                     item.setNbtData(null);
-                return tool;
+                }
+                return null;
             }
             nbt = new CompoundTag(map = new HashMap<>());
         } else {