Fix application can't exit bug

src/main.cpp

@@ -52,13 +52,15 @@ int main(int argc, char* argv[])
     SQLHelper::Open();
     MainWindow w;
     w.showFullScreen();
-    LoginWindow l;
-    needLogin:
-    l.showFullScreen();
-    int rec =  l.exec();
-    if (rec !=QDialog::Accepted )
     {
-        return 0;
+
+        LoginWindow l;
+        needLogin:
+        l.showFullScreen();
+        int rec = l.exec();
+        if (rec != QDialog::Accepted) {
+            return 0;
+        }
     }
 //    l.deleteLater();
     w.centerWidgetShow();