Fix empty and zero values parsing part 2

Signed-off-by: Andrey Berezin <a.berezin@yadro.com>

src/frostfs_testlib/load/load_config.py

@@ -277,7 +277,7 @@ class LoadParams:
         fields_with_data = [
             MetaField(field.metadata, getattr(instance, field.name))
             for field in data_fields
-            if field.metadata and getattr(instance, field.name)
+            if field.metadata and getattr(instance, field.name) is not None
         ]
 
         for field in data_fields: