Fix surfaces with single color for all faces/vertices
Fix surfaces with single color for all faces/vertices

Fix surfaces with single color for all faces/vertices that still have
an indexed color set that is not used by Matlab due to specified single
solid color. (Example: create streamtube, apply color to streamtube,
matlab plots stream tube (correctly) in the set color but fig2idtf
generates an index color stream tube cycling through the complete
colormap without this fix)

adhusch/fig2u3d