configuration: fix glitch when changing versions

lib/solaar/configuration.py

@@ -84,7 +84,8 @@ def _parse_config(loaded_config, config_path):
         loaded_version = loaded_config[0]
         discard_derived_properties = loaded_version != current_version
         if discard_derived_properties:
-            _log.warning(
+            if _log.isEnabledFor(_INFO):
+                _log.info(
                     'config file \'%s\' was generated by another version of solaar '
                     '(config: %s, current: %s). refreshing detected device capabilities', config_path, loaded_version,
                     current_version
@@ -112,8 +113,8 @@ def _device_entry_from_config_dict(data, discard_derived_properties):
         # remove any string entries (from bad conversions)
         data['divert-keys'] = {k: v for k, v in divert.items() if isinstance(k, int)}
     if discard_derived_properties:
-        data.pop('_absent')
-        data.pop('_battery')
+        data.pop('_absent', None)
+        data.pop('_battery', None)
     return _DeviceEntry(**data)