Fix memory leak found by copilot

Co-authored-by: softins <softins@users.noreply.github.com>
See: #3702

Author: ann0see

src/clientdlg.cpp

@@ -876,7 +876,13 @@ void CClientDlg::OnChatTextReceived ( QString strChatText )
 {
     if ( pSettings->bEnableAudioAlerts )
     {
-        QSoundEffect* sf = new QSoundEffect();
+        QSoundEffect* sf = new QSoundEffect ( this );
+        connect ( sf, &QSoundEffect::playingChanged, this, [sf]() {
+            if ( !sf->isPlaying() )
+            {
+                sf->deleteLater();
+            }
+        } );
         sf->setSource ( QUrl::fromLocalFile ( ":sounds/res/sounds/new_message.wav" ) );
         sf->play();
     }
@@ -927,7 +933,13 @@ void CClientDlg::OnNumClientsChanged ( int iNewNumClients )
 {
     if ( pSettings->bEnableAudioAlerts && iNewNumClients > iClients )
     {
-        QSoundEffect* sf = new QSoundEffect();
+        QSoundEffect* sf = new QSoundEffect ( this );
+        connect ( sf, &QSoundEffect::playingChanged, this, [sf]() {
+            if ( !sf->isPlaying() )
+            {
+                sf->deleteLater();
+            }
+        } );
         sf->setSource ( QUrl::fromLocalFile ( ":sounds/res/sounds/new_user.wav" ) );
         sf->play();
     }