Undo button undoes several context definitions

[eric-laporte]

Clicking the undo button undoes several context definitions instead of undoing the latest one only.

What steps will reproduce the problem?

1. Create a graph with several boxes.
2. Use the green icons for context on several boxes, to define several contexts (left, right, negative right).
3. Click the undo button.

What is the expected output?

The undo button could cancel the latest defined context.

What do you see instead?

The undo button cancels all the contexts.

More info

• Unitex/GramLab IDE version: 3.3.7
• UnitexToolLogger version: 4.0.0
• Did this work before?: [ ] yes [x] no