Fix create_transcription_entity assertions

arkindex_worker/worker/entity.py

@@ -93,10 +93,10 @@ class EntityMixin(object):
             entity, str
         ), "entity shouldn't be null and should be of type str"
         assert (
-            offset and isinstance(offset, int) and offset >= 0
+            offset is not None and isinstance(offset, int) and offset >= 0
         ), "offset shouldn't be null and should be a positive integer"
         assert (
-            length and isinstance(length, int) and length > 0
+            length is not None and isinstance(length, int) and length > 0
         ), "length shouldn't be null and should be a strictly positive integer"
         if self.is_read_only:
             logger.warning(