Creating a new window from contour enables bell despite it being disabled in the config

[herrhotzenplotz]

This happens on both master and the latest release.

I don't like the bell sound - thus I disabled it by setting the bell sound to "off" in the configuration file. When I hit Ctrl+Shift+n to open a new contour window the bell sound suddenly is enabled and starts annoying me.

The bell sound should be kept disabled.