[chronojump] Precaution: do not allow to forceSensor capture if no session or no person

[Xavier de Blas <xaviblas src gnome org>]

commit b3c212a542c11b8c529f75f58e551f7452bd3ca1
Author: Xavier de Blas <xaviblas gmail com>
Date:   Mon May 3 15:07:32 2021 +0200

    Precaution: do not allow to forceSensor capture if no session or no person

 src/gui/app1/forceSensor.cs | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/src/gui/app1/forceSensor.cs b/src/gui/app1/forceSensor.cs
index fb4e5947..f3adfaea 100644
--- a/src/gui/app1/forceSensor.cs
+++ b/src/gui/app1/forceSensor.cs
@@ -1146,6 +1146,10 @@ public partial class ChronoJumpWindow
 
        private void forceSensorCaptureDo()
        {
+               //precaution
+               if (currentSession == null || currentPerson == null)
+                       return;
+
                lastChangedTime = 0;
 
                if(! forceSensorSendCommand("start_capture:", "Preparing capture...", "Catched force 
capturing"))