Bugs in Marching Cube test for 3D Viewer (javax.media.j3d.CapabilityNotSetException) was fixed.
In the method "displayCase", removal of BranchGroups is done after
checking if the child object is an instance of BranchGroup and also is
detachable. A small bug that causeed a warning message "Case X already
exists" when slider is moved is also fixed, by removing all contents
before adding a new Mesh content.

Leading spaces changed to tabs, to follow the convention.

Another indent fixed