Skip non-frontend themes in config option

Author: jissereitsma

Config/Source/ThemePathOptions.php

@@ -2,6 +2,7 @@
 
 namespace Loki\Theme\Config\Source;
 
+use Magento\Framework\App\Area;
 use Magento\Framework\Data\OptionSourceInterface;
 use Magento\Framework\View\Design\Theme\ThemeList;
 use Magento\Framework\View\Design\ThemeInterface;
@@ -18,6 +19,10 @@ public function toOptionArray()
         $options = [];
         foreach ($this->themeList->getItems() as $theme) {
             /** @var ThemeInterface $theme */
+            if ($theme->getArea() !== Area::AREA_FRONTEND) {
+                continue;
+            }
+
             $options[] = [
                 'value' => $theme->getThemePath(),
                 'label' => $theme->getThemePath(),