Ticket #23181: 23181.patch

wp-admin/custom-header.php

@@ -1009 +1009 @@
                 }
 
                 set_theme_mod( 'header_image', $default );
-                set_theme_mod( 'header_image_data', (object) $default_data );
+                if ( ! empty( $default_data ) )
+                        set_theme_mod( 'header_image_data', (object) $default_data );
         }
 }