uncaught exception: Formula associated to digest not found.

in file: /var/www/html/filter/wiris/integration/lib/com/wiris/plugin/impl/RenderImpl.class.php line 191
#0 /var/www/html/filter/wiris/integration/showimage.php(46): com_wiris_plugin_impl_RenderImpl->showImage('fd10b303231b0ba...', NULL, Object(filter_wiris_paramsprovider)) #1 {main}