Merge pull request #3732 from VesnaT/fix_on_selection_changed

[FIX] LinearProjectionVizRank: Add a necessary check

Author: janezd

Orange/widgets/visualize/owlinearprojection.py

@@ -164,6 +164,8 @@ def row_for_state(self, score, state):
         return [item]
 
     def on_selection_changed(self, selected, deselected):
+        if not selected.indexes():
+            return
         attrs = selected.indexes()[0].data(self._AttrRole)
         self.selectionChanged.emit([attrs])