bugfix in index calculation for material group > 0

WFObj.cc

@@ -571,7 +571,7 @@ void WFObj::draw()
         renderMaterial(m_materials[it->first]);
         glDrawElements(GL_TRIANGLES, m_face_indices[it->first].second,
                 GL_UNSIGNED_SHORT,
-                (GLvoid *) (sizeof(GLfloat) * m_face_indices[it->first].first));
+                (GLvoid *) (sizeof(GLshort) * m_face_indices[it->first].first));
         glPopAttrib();
     }
     glPopClientAttrib();