fix: crash on app exit due to running thread

https://doc.qt.io/qt-6/qthread.html\#dtor.QThread

src/broadcaster.cpp

@@ -104,9 +104,10 @@ Broadcaster::Broadcaster(QObject *parent) : QObject(parent)
 
 Broadcaster::~Broadcaster()
 {
-  if (m_worker)
+  if (m_worker && m_worker->isRunning())
   {
     m_worker->requestInterruption();
+    m_worker->wait();
   }
 }