JSXC : display problem

Hello,

I can see a problem with the display of JSXC (see in attached file)

It is like if there's no CSS.

i use a RPI3, with a buster debian https://people.debian.org/~stapelberg/raspberrypi3/2018-01-08/ i installed it the last week.

plinth version : 0.29.1 ejabberd : 18.03-2 arm64 freedombox-setup : 0.12 libjs-jsxc : 3.0.0+dfsg3-2

thanks if you can watch for this problem.