[chronojump] Fixed not seeing error label on forceSensorExercise create without name

[Xavier de Blas <xaviblas src gnome org>]

commit 29a9449d0c0241a120919f079b6a01cca1002aa7
Author: Xavier de Blas <xaviblas gmail com>
Date:   Tue Jun 22 17:15:38 2021 +0200

    Fixed not seeing error label on forceSensorExercise create without name

 src/gui/forceSensorExercise.cs | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/gui/forceSensorExercise.cs b/src/gui/forceSensorExercise.cs
index 4b0e427f6..e345983ca 100644
--- a/src/gui/forceSensorExercise.cs
+++ b/src/gui/forceSensorExercise.cs
@@ -145,6 +145,7 @@ public class ForceSensorExerciseWindow
                        UtilGtk.WindowColor(force_sensor_exercise, Config.ColorBackground);
                        UtilGtk.ContrastLabelsLabel (Config.ColorBackgroundIsDark, label_header);
                        UtilGtk.ContrastLabelsLabel (Config.ColorBackgroundIsDark, label_help);
+                       UtilGtk.ContrastLabelsLabel (Config.ColorBackgroundIsDark, label_error);
                        UtilGtk.ContrastLabelsLabel (Config.ColorBackgroundIsDark, 
label_radio_desc_examples_desc);
                        UtilGtk.ContrastLabelsLabel (Config.ColorBackgroundIsDark, 
label_radio_desc_examples_examples);
                }