Getting below error during first time enable and set default.
Drupal\Core\Config\ConfigValueException: table.1.font_head_family key contains a dot which is not supported. in Drupal\Core\Config\ConfigBase->validateKeys() (line 211 of core/lib/Drupal/Core/Config/ConfigBase.php).
Drupal\Core\Config\ConfigBase->setData(Array) (Line: 107)
Drupal\Core\Config\Config->setData(Array) (Line: 360)
Drupal\Core\Config\ConfigInstaller->createConfiguration('', Array) (Line: 148)
Drupal\Core\Config\ConfigInstaller->installDefaultConfig('theme', 'dempo') (Line: 75)
Drupal\Core\ProxyClass\Config\ConfigInstaller->installDefaultConfig('theme', 'dempo') (Line: 237)
Drupal\Core\Extension\ThemeInstaller->install(Array) (Line: 225)
Drupal\system\Controller\ThemeController->setDefaultTheme(Object)
call_user_func_array(Array, Array) (Line: 123)
Fixed
2.0
Code
@ravi Kant I installed it locally on version 2.0.18 I did not get the error. Can you provide more details to reproduce the error.
The issue is appearing during first time enable theme. If you have already enabled and disabled then issue will not appear.
Completely uninstall and do "Enable and set default"