Issue #2890514 by quietone, vomitHatSteve, heddn: upgrade_d6_imagecache_presets fails if blank "action" is enountered

core/modules/image/src/Plugin/migrate/process/d6/ImageCacheActions.php

@@ -20,6 +20,9 @@ class ImageCacheActions extends ProcessPluginBase {
     $effects = [];
 
     foreach ($row->getSourceProperty('actions') as $action) {
+      if (empty($action['action'])) {
+        continue;
+      }
       $id = preg_replace('/^imagecache/', 'image', $action['action']);
 
       if ($id === 'image_crop') {

core/modules/migrate_drupal/tests/fixtures/drupal6.php

@@ -10645,6 +10645,14 @@ $connection->insert('imagecache_action')
   'action' => 'imagecache_rotate',
   'data' => 'a:3:{s:7:"degrees";s:2:"55";s:6:"random";i:0;s:7:"bgcolor";s:0:"";}',
 ))
+  ->values(array(
+  'actionid' => '7',
+  'presetid' => '2',
+  'weight' => '0',
+  'module' => 'imagecache',
+  'action' => '',
+  'data' => 'a:3:{s:7:"degrees";s:2:"55";s:6:"random";i:0;s:7:"bgcolor";s:0:"";}',
+  ))
 ->execute();
 $connection->schema()->createTable('imagecache_preset', array(
   'fields' => array(