Added a check to see if the material selection is empty. In this case it now generates a warning telling the user of the likely causes of the problem.
Added a check to see if the material selection is empty. In this case it now generates a warning telling the user of the likely causes of the problem.

alunmorgan/GdfidL-framework,alunmorgan/EM-modellling-framework,alunmorgan/GdfidL-framework