when I attempt to use the editor module and outline the corpus callosum as instructed in the DTI analysis tutoria, the tractography does not display itself in the 3d viewer. After I outline the corpus callosum, set all of the right parameters and settings, and click apply, Slicer informs me that the status is "Completed with errors" instead of "Completed", and no tractography results are shown. attached in a screenshot of what happens when I try to complete this step.