set fallback= for ini parser

mypy_django_plugin/config.py

@@ -16,10 +16,9 @@ class Config:
         if not ini_config.has_section('mypy_django_plugin'):
             raise ValueError('Invalid config file: no [mypy_django_plugin] section')
 
-        django_settings = ini_config.get('mypy_django_plugin', 'django_settings')
-        if type(django_settings) == object:
-            django_settings = None
-        else:
+        django_settings = ini_config.get('mypy_django_plugin', 'django_settings',
+                                         fallback=None)
+        if django_settings:
             django_settings = django_settings.strip()
 
         return Config(django_settings_module=django_settings,