ISTWCMS-7131: don't try to check keys that aren't set

src/Service/UwBlockManualElements.php

@@ -262,12 +262,13 @@ class UwBlockManualElements {
     // If we are not updating a block, we have to get the node ids
     // from the block config.
     if (!$updating_block) {
+      if (isset($config[$name])) {
+        // Get the  ids from the block config.
+        $ids = $config[$name][$ids_name];
 
-      // Get the  ids from the block config.
-      $ids = $config[$name][$ids_name];
-
-      // Set the ids into the form state.
-      $form_state->set($ids_name, $ids);
+        // Set the ids into the form state.
+        $form_state->set($ids_name, $ids);
+      }
     }
     // If we are on updating a block, get the ids from the form_state.
     else {