Merge branch '0.80.x' into service-mode-refactor-0.80

mpf/core/config_validator.py

@@ -356,7 +356,7 @@ def _validate_type_subconfig(self, item, param, validation_failure_info):
         # The inclusion of sound_pools causes a nested ducking subconfig that
         # fails due to missing required properties. Check for an empty dict
         # as subconfig and ignore it.
-        if item is None or not len(item):
+        if item is None or (item is Dict and not len(item)):
             return {}
         try:
             attribute, base_spec_str = param.split(",", 1)