fix: extra check for entity schema (#138)

lib/push/push-to-space.js

@@ -284,7 +284,7 @@ export default function pushToSpace ({
 // In case some entity throws an error, we null it in the list to avoid further processing.
 // This functions removes the nulled entities from the lists.
 function removeEmptyEntities (entityList) {
-  return entityList.filter((entity) => entity !== null)
+  return entityList.filter((entity) => !!entity && entity.sys)
 }
 
 function archiveEntities (ctx, task, entities, sourceEntities) {