Merge branch 'fix-mask-path-registration' into 'staging'

Fixing handling of potentially non existing masks

See merge request !41

core/registrar/backend.py

@@ -211,12 +211,13 @@ class EOxServerBackend(Backend):
 
         # register masks
         for mask_identifier, mask_type_name in mapping.get('masks', {}).items():
-            _, mask_item = source.get_container_and_path(item.mask_files.get(mask_identifier))
+            mask_item = item.mask_files.get(mask_identifier)
             if mask_item:
+                _, mask_path = source.get_container_and_path()
                 logger.info(f"Adding mask (file) {mask_type_name} to product")
                 MaskRegistrator().register(
                     product.identifier,
-                    storage + [mask_item],
+                    storage + [mask_path],
                     mask_type_name,
                 )