[chronojump] Fixed forceSensor analyze crash on click []B after zoom

[Xavier de Blas <xaviblas src gnome org>]

commit 567592e16158d5ef40eb14aadaf05e2bdd721369
Author: Xavier de Blas <xaviblas gmail com>
Date:   Mon Dec 9 13:42:53 2019 +0100

    Fixed forceSensor analyze crash on click []B after zoom

 src/gui/forceSensorAnalyze.cs | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/src/gui/forceSensorAnalyze.cs b/src/gui/forceSensorAnalyze.cs
index 8a18d878..3b0f2fca 100644
--- a/src/gui/forceSensorAnalyze.cs
+++ b/src/gui/forceSensorAnalyze.cs
@@ -851,9 +851,13 @@ public partial class ChronoJumpWindow
                forceSensorZoomApplied = ! forceSensorZoomApplied;
 
                if(forceSensorZoomApplied)
+               {
                        button_force_sensor_ai_zoom.Label = "Zoom out";
-               else
+                       checkbutton_force_sensor_ai_b.Sensitive = false;
+               } else {
                        button_force_sensor_ai_zoom.Label = "Zoom [A-B]";
+                       checkbutton_force_sensor_ai_b.Sensitive = true;
+               }
 
                //store hscale a to help return to position on unzoom
                if(forceSensorZoomApplied) {
@@ -882,7 +886,8 @@ public partial class ChronoJumpWindow
                bool debug = false;
 
                button_force_sensor_image_save_rfd_manual.Sensitive = true;
-               checkbutton_force_sensor_ai_b.Sensitive = true;
+               if(! forceSensorZoomApplied)
+                       checkbutton_force_sensor_ai_b.Sensitive = true;
                if(checkbutton_force_sensor_ai_b.Active)
                        button_force_sensor_analyze_AB_save.Visible = true;