Merge pull request #1675 from nikicc/owtable-empty-sparse

[FIX] TableModel: Don't crash on empty sparse data

Author: ajdapretnar

Orange/widgets/utils/itemmodels.py

@@ -885,23 +885,23 @@ def make_column(var, role):
 
         columns = []
 
-        if self.Y_density != Storage.DENSE:
+        if self.Y_density != Storage.DENSE and domain.class_vars:
             coldesc = make_basket(domain.class_vars, self.Y_density,
                                   TableModel.ClassVar)
             columns.append(coldesc)
         else:
             columns += [make_column(var, TableModel.ClassVar)
                         for var in domain.class_vars]
 
-        if self.M_density != Storage.DENSE:
+        if self.M_density != Storage.DENSE and domain.metas:
             coldesc = make_basket(domain.metas, self.M_density,
                                   TableModel.Meta)
             columns.append(coldesc)
         else:
             columns += [make_column(var, TableModel.Meta)
                         for var in domain.metas]
 
-        if self.X_density != Storage.DENSE:
+        if self.X_density != Storage.DENSE and domain.attributes:
             coldesc = make_basket(domain.attributes, self.X_density,
                                   TableModel.Attribute)
             columns.append(coldesc)