wxGUI/animation: color of isosurface should match the volume (merged from trunk, https://trac.osgeo.org/grass/changeset/59616)

git-svn-id: https://svn.osgeo.org/grass/grass/branches/releasebranch_7_0@59617 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/animation/nviztask.py

@@ -250,6 +250,8 @@ class NvizTask:
             # FIXME: we assume we want always default color map
             if paramName == 'elevation_map':
                 self.task.set_param('color_map', '')
+            if paramName == 'volume':
+                self.task.set_param('isosurf_color_map', '')
             self.task.set_flag('overwrite', True)
             self.task.set_param('output', 'tobechanged')
             cmd = self.task.get_cmd(ignoreErrors=False, ignoreRequired=False, ignoreDefault=True)