fix compilation on gcc

src/util/QObjectRef.hpp

@@ -66,8 +66,9 @@ private:
         // new
         if (other)
         {
-            this->conn_ = QObject::connect(
+            // the cast here should absolutely not be necessary, but gcc still requires it
-                other, &QObject::destroyed, qApp,
+            this->conn_ =
+                QObject::connect((QObject *)other, &QObject::destroyed, qApp,
                                  [this](QObject *) { this->set(nullptr); },
                                  Qt::DirectConnection);
         }