Showing empty page if erroreously no sitemap exists in the db instead of php error.

src/Controller/SimplesitemapController.php

@@ -19,7 +19,8 @@ class SimplesitemapController {
    * Returns the whole sitemap, a requested sitemap chunk, or the sitemap index file.
    *
    * @param int $sitemap_id
-   *  Id of the sitemap chunk.
+   *  Optional ID of the sitemap chunk. If none provided, the first chunk or
+   *  the sitemap index is fetched.
    *
    * @return object Response
    *  Returns an XML response.
@@ -27,6 +28,7 @@ class SimplesitemapController {
   public function get_sitemap($sitemap_id = NULL) {
     $sitemap = new Simplesitemap;
     $output = $sitemap->get_sitemap($sitemap_id);
+    $output = !$output ? '' : $output;
 
     // Display sitemap with correct xml header.
 //    return new CacheableResponse($output, Response::HTTP_OK, array('content-type' => 'application/xml'));

src/Simplesitemap.php

@@ -153,10 +153,12 @@ class Simplesitemap {
 
       // Return sitemap if there is only one chunk.
       else {
-        return $this->sitemap[1]->sitemap_string;
+        if (isset($this->sitemap[1])) {
+          return $this->sitemap[1]->sitemap_string;
+        }
+        return FALSE;
       }
     }
-
     // Return specific sitemap chunk.
     else {
       return $this->sitemap[$sitemap_id]->sitemap_string;
@@ -177,7 +179,6 @@ class Simplesitemap {
   /**
    * Saves the sitemap to the db.
    */
-//  private function save_sitemap() {
   public static function save_sitemap($values) {
     db_insert('simple_sitemap')
     ->fields(array(