fix(config): Check both for empty string and None

Author: ferdinandjarisch

src/gallia/command/config.py

@@ -438,7 +438,9 @@ def attributes_from_config(cls, config: Config, source: str = "config file") ->
             for name, info in original_infos.items():
                 if isinstance(info, ConfigArgFieldInfo):
                     config_attribute = (
-                        f"{info.config_section}.{name}" if info.config_section != "" else name
+                        f"{info.config_section}.{name}"
+                        if info.config_section not in ("", None)
+                        else name
                     )
 
                     if (value := config.get_value(config_attribute)) is not None: