OWFeatureStatistics: Fix crash on discrete variables with no values

Author: pavlin-policar

Orange/widgets/data/owfeaturestatistics.py

@@ -500,7 +500,7 @@ def data(self, index, role):
             if role == Qt.DisplayRole:
                 if isinstance(attribute, DiscreteVariable):
                     output = self._center[row]
-                    if not np.isnan(output):
+                    if not np.isnan(output) and len(attribute.values) > 0:
                         output = attribute.str_val(self._center[row])
                 elif isinstance(attribute, TimeVariable):
                     output = attribute.str_val(self._center[row])
@@ -515,7 +515,7 @@ def data(self, index, role):
         elif column == self.Columns.MIN:
             if role == Qt.DisplayRole:
                 if isinstance(attribute, DiscreteVariable):
-                    if attribute.ordered:
+                    if attribute.ordered and len(attribute.values) > 0:
                         output = attribute.str_val(self._min[row])
                 elif isinstance(attribute, TimeVariable):
                     output = attribute.str_val(self._min[row])
@@ -524,7 +524,7 @@ def data(self, index, role):
         elif column == self.Columns.MAX:
             if role == Qt.DisplayRole:
                 if isinstance(attribute, DiscreteVariable):
-                    if attribute.ordered:
+                    if attribute.ordered and len(attribute.values) > 0:
                         output = attribute.str_val(self._max[row])
                 elif isinstance(attribute, TimeVariable):
                     output = attribute.str_val(self._max[row])

Orange/widgets/data/tests/test_owfeaturestatistics.py

@@ -40,6 +40,12 @@
     continuous_same
 ]
 
+# Discrete variable with no values
+empty_discrete = VarDataPair(
+    DiscreteVariable("empty discrete", values=[]),
+    np.array([np.nan] * 5, dtype=float),
+)
+
 # Unordered discrete variable variations
 rgb_full = VarDataPair(
     DiscreteVariable('rgb_full', values=['r', 'g', 'b']),
@@ -251,6 +257,13 @@ def test_on_data_with_continuous_values_all_the_same(self, prepare_table):
         self.send_signal('Data', prepare_table(data))
         self.run_through_variables()
 
+    @table_dense_sparse
+    def test_on_data_with_discrete_with_no_values(self, prepare_table):
+        data = make_table([empty_discrete, ints_same])
+        self.send_signal(self.widget.Inputs.data, prepare_table(data))
+        self.force_render_table()
+        self.run_through_variables()
+
 
 def select_rows(rows: List[int], widget: OWFeatureStatistics):
     """Since the widget sorts the rows, selecting rows isn't trivial."""