fix crash when closing a project after using fitting activitiy

GUI/View/Fit/FitSessionManager.cpp

@@ -22,6 +22,12 @@ FitSessionManager::FitSessionManager(QObject* parent) : QObject(parent), m_activ
 {
 }
 
+FitSessionManager::~FitSessionManager()
+{
+    for (auto* jobItem : m_item_to_controller.keys())
+        jobItem->mapper()->unsubscribe(this);
+}
+
 FitSessionController* FitSessionManager::sessionController(JobItem* item)
 {
     FitSessionController* result(nullptr);

GUI/View/Fit/FitSessionManager.h

@@ -29,6 +29,7 @@ class FitSessionManager : public QObject {
     Q_OBJECT
 public:
     FitSessionManager(QObject* parent = nullptr);
+    ~FitSessionManager();
 
     FitSessionController* sessionController(JobItem* item);