Fix MacOS crash issue

src/controller.cpp

@@ -216,13 +216,24 @@ void Controller::refreshRescanStatus() {
 }
 
 void Controller::closeRefreshStatusIfAlive() {
-    if (rescanProgress) {
-        delete rescanProgress;
-        rescanProgress = nullptr;
+    // For some bizare reason, this function is re-entering on MacOS. That is, while
+    // "delete rescanProgress" is executing, this function gets called again, on the same
+    // thread. So use a mutex to prevent double deletes
+    static QMutex progressDeleteLock(QMutex::NonRecursive);
 
-        // Update the status bar
-        ui->statusBar->showMessage(QObject::tr("Rescan finished"));
+    if (progressDeleteLock.tryLock()) {
+        if (rescanProgress) {
+            rescanProgress->closeProgress();
+            delete rescanProgress;
+            rescanProgress = nullptr;        
+
+            // Update the status bar
+            ui->statusBar->showMessage(QObject::tr("Rescan finished"));
+        }
+
+        progressDeleteLock.unlock();
     }
+
 }
 
 /// This will refresh all the balance data from zcashd

src/rescanprogress.cpp

@@ -14,11 +14,14 @@ RescanProgress::RescanProgress(MainWindow* _main)
 }
 
 RescanProgress::~RescanProgress() {
-    progress->setValue(100);
-    progress->deleteLater();
+    delete progress;
 }
 
 void RescanProgress::updateProgress(int tick) {
     if (tick >= 0 && tick < 100)
         progress->setValue(tick);
-}
+}
+
+void RescanProgress::closeProgress() {
+    progress->setValue(100);
+}

src/rescanprogress.h

@@ -10,7 +10,8 @@ class RescanProgress {
     ~RescanProgress();
 
     void updateProgress(int value);
-
+    void closeProgress();
+
 private:
     MainWindow* main;
     QProgressDialog* progress;