[chronojump] Fix on forceSensorExercise combo when last exercise is deleted

[Xavier de Blas <xaviblas src gnome org>]

commit 685fc92ee98fbd70869ba0ada6b632cec5d7ade1
Author: Xavier de Blas <xaviblas gmail com>
Date:   Tue Sep 17 18:07:29 2019 +0200

    Fix on forceSensorExercise combo when last exercise is deleted

 src/gui/forceSensor.cs | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/gui/forceSensor.cs b/src/gui/forceSensor.cs
index da73bc04..625b729f 100644
--- a/src/gui/forceSensor.cs
+++ b/src/gui/forceSensor.cs
@@ -2046,6 +2046,8 @@ LogB.Information(" re R ");
                if(forceSensorExercises.Count == 0)
                {
                        forceSensorComboExercisesString = new String [0];
+                       UtilGtk.ComboUpdate(combo_force_sensor_exercise, new String[0], "");
+
                        return;
                }