Don't return invalid directories if they're in the options.ini file

kolibri/core/device/models.py

@@ -22,6 +22,7 @@
 from kolibri.deployment.default.sqlite_db_names import SYNC_QUEUE
 from kolibri.plugins.app.utils import interface
 from kolibri.utils.conf import OPTIONS
+from kolibri.utils.filesystem import check_is_directory
 from kolibri.utils.options import update_options_file
 
 device_permissions_fields = ["is_superuser", "can_manage_content"]
@@ -168,7 +169,9 @@ def primary_storage_location(self, value):
 
     @property
     def secondary_storage_locations(self):
-        return OPTIONS["Paths"]["CONTENT_FALLBACK_DIRS"]
+        return list(
+            filter(check_is_directory, OPTIONS["Paths"]["CONTENT_FALLBACK_DIRS"])
+        )
 
     @secondary_storage_locations.setter
     def secondary_storage_locations(self, value):