Issue #3502748 by sundhar: LogicException: Cannot create key "loading"

Closes #3502748

src/Media/BlazyResponsiveImage.php

@@ -173,9 +173,11 @@ class BlazyResponsiveImage {
       ->set('ratios', (object) $ratios)
       ->set('resimage.ids', array_values($names));
 
-    // Only needed the last one.
-    // Overrides plain old image dimensions.
-    $blazies->set('image', end($dimensions), TRUE);
+    if ($dimensions) {
+      // Only needed the last one.
+      // Overrides plain old image dimensions.
+      $blazies->set('image', end($dimensions), TRUE);
+    }
 
     // Currently only needed by Preload.
     // @todo phpstan bug, misleading with multiple conditions.