Fix GTK icon issue

Dockerfile

@@ -283,6 +283,7 @@ RUN if [ "${UBUNTU_RELEASE}" \< "20.04" ]; then add-apt-repository -y ppa:cyberm
 
 # Install latest selkies-gstreamer (https://github.com/selkies-project/selkies-gstreamer) build, Python application, and web application, should be consistent with selkies-gstreamer documentation
 RUN apt-get update && apt-get install --no-install-recommends -y \
+        adwaita-icon-theme-full \
         build-essential \
         python3-pip \
         python3-dev \