fix compilation on gcc

src/util/QObjectRef.hpp

@@ -66,10 +66,11 @@ private:
         // new
         if (other)
         {
-            this->conn_ = QObject::connect(
-                other, &QObject::destroyed, qApp,
-                [this](QObject *) { this->set(nullptr); },
-                Qt::DirectConnection);
+            // the cast here should absolutely not be necessary, but gcc still requires it
+            this->conn_ =
+                QObject::connect((QObject *)other, &QObject::destroyed, qApp,
+                                 [this](QObject *) { this->set(nullptr); },
+                                 Qt::DirectConnection);
         }
 
         this->t_ = other;