Firefox, how to get rid of message "Activate mozplugger handles quicktime and windows media player"?

I use mozplugger in firefox in order to use some plugins like okular (I don't like acroread embedded).
I've been using it sinc long time ago, but now since some update each time i open a pdf in firefox a message "Activate mozplugger handles quicktime and windows media player" apears and i have to choose ALLOW now or allow always for each site.

Is it possible to say firefox i want always open PDF with okular without any question?

regards