Fix NPE when retrieving an entity with a null UUID

While the null UUID is almost certainly an error, the old
implementation did not NPE as it used a plain HashMap for lookup
by UUID, whereas we use a ConcurrentHashMap which will NPE on
null keys.

src/main/java/ca/spottedleaf/moonrise/patches/chunk_system/level/entity/EntityLookup.java

@@ -88,15 +88,15 @@ public Entity get(final int id) {
 
     @Override
     public Entity get(final UUID id) {
-        return maskNonAccessible(this.entityByUUID.get(id));
+        return maskNonAccessible(id == null ? null : this.entityByUUID.get(id));
     }
 
     public boolean hasEntity(final UUID uuid) {
         return this.get(uuid) != null;
     }
 
     public String getDebugInfo() {
-        return "count_id:" + this.entityById.size() + ",count_uuid:" + this.entityByUUID.size() + ",region_count:" + this.regions.size();
+        return "count_id:" + this.entityById.size() + ",count_uuid:" + this.entityByUUID.size() + ",count_accessible:" + this.getEntityCount() + ",region_count:" + this.regions.size();
     }
 
     protected static final class ArrayIterable<T> implements Iterable<T> {