[Plugin: qTranslate] Post page error

Hello, I get an error on post page view on my web

Catchable fatal error: Object of class WP_Post could not be converted to string in …. /wp/wp-content/plugins/qtranslate/qtranslate_core.php on line 455

content of that post and the rest of the web is not loaded as well – example: https://www.drahos-karoserie.cz/aktualni-prace/?lang=en

Also I have error message on post edit page saying something like “qTranslator was disabled because it was not tested with actual wordpress version…”

I’m facing this issue since some WP update, but I’m not sure since which one. I’ve tested version 3.9.1 also and the error still presists.

Can you help me with that?