#75: User prompt if no theme is chosen and bail out so we don't get a…

…n error.

kalastatic.module

@@ -8,6 +8,7 @@
 use Symfony\Component\Finder\Finder;
 use Symfony\Component\Yaml\Parser;
 use Symfony\Component\Filesystem\Filesystem;
+use Drupal\Core\Url;
 
 /**
  * Implements hook_preprocess().
@@ -71,6 +72,13 @@ function kalastatic_page_attachments(array &$attachments) {
   $ks_themes = $module_settings->get('kalastatic_theme_list');
   $active_theme = \Drupal::service('theme.manager')->getActiveTheme()->getName();
 
+  if ($ks_themes == NULL) {
+    // Set a message and bail out if no themes have been chosen.
+    $settings_url = Url::fromRoute('kalastatic.settings');
+    drupal_set_message(t('Kalastatic requires you to choose the theme(s) you would like it to work with. Go to the <a href="@link">settings page.</a>', array('@link' => $settings_url->toString())), 'error');
+    return;
+  }
+
   // Check if the active theme has been chosen.
   if (in_array($active_theme, $ks_themes)) {
     // Attach library to this page.

src/Form/KalastaticSettingsForm.php

@@ -48,6 +48,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     foreach ($themes as $mn => $theme) {
       $theme_list[$mn] = $theme->info['name'];
     }
+    $theme_list_default = $config->get('kalastatic_theme_list') ?: [];
 
     $form = [
       'description' => [
@@ -71,7 +72,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
         '#type' => 'checkboxes',
         '#title' => $this->t('Include Kalastatic assets for'),
         '#options' => $theme_list,
-        '#default_value' => $config->get('kalastatic_theme_list'),
+        '#default_value' => $theme_list_default,
         '#description' => $this->t('The CSS and Javascript output by Kalastatic will be included when any of the chosen themes are set as the default theme.'),
       ],
       'kalastatic_brand_color' => [