Apply saved optional to column with the optional attribute

If the same column is added twice in a view with and without optional, only the
columns with optional attribute must be updated.

sao/src/view/tree.js

@@ -826,8 +826,9 @@
                     return;
                 }
                 var optional;
-                if (Object.prototype.hasOwnProperty.call(
-                    tree_column_optional, name)) {
+                if ((column.attributes.optional) &&
+                    Object.prototype.hasOwnProperty.call(
+                        tree_column_optional, name)) {
                     optional = tree_column_optional[name];
                 } else {
                     optional = Boolean(parseInt(

tryton/tryton/gui/window/view_form/view/list.py

@@ -1166,7 +1166,8 @@ class ViewTree(View):
                 continue
             widget = self.get_column_widget(column)
             widget.set_editable()
-            if column.name in tree_column_optional:
+            if ('optional' in widget.attrs
+                    and column.name in tree_column_optional):
                 optional = tree_column_optional[column.name]
             else:
                 optional = bool(int(widget.attrs.get('optional', '0')))