webglapp.js: fix errors when coloring by user or reviewer.
webglapp.js: fix errors when coloring by user or reviewer.

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