webglapp: fix removal of skeleton text labels and label spheres.
webglapp: fix removal of skeleton text labels and label spheres.

fzadow/CATMAID,htem/CATMAID,fzadow/CATMAID,htem/CATMAID,fzadow/CATMAID,htem/CATMAID,fzadow/CATMAID,htem/CATMAID