Colorbar only available for glyphset

[GoogleCodeExporter]

The 'render colormap' option only works when a glyphset with connectivity data 
is loaded, and not when a surface set is loaded on its own. The colorbar also 
disappears when you switch off the visibility of the glyphset.

To reproduce:

Load a nifti, glyphset, and surface set. Toggle visibility of glyphset and 
notice that the colorbar toggles on and off too.

Original issue reported on code.google.com by [email protected] on 20 Jan 2014 at 9:43