fixed crash when changing theme after closing tab

src/widgets/helper/signallabel.hpp

@@ -11,7 +11,7 @@ class SignalLabel : public QLabel
 
 public:
     explicit SignalLabel(QWidget *parent = nullptr, Qt::WindowFlags f = 0);
-    ~SignalLabel() override = default;
+    virtual ~SignalLabel() override = default;
 
 signals:
     void mouseDoubleClick(QMouseEvent *ev);

src/widgets/helper/splitheader.hpp

@@ -29,7 +29,7 @@ class SplitHeader : public BaseWidget
 
 public:
     explicit SplitHeader(Split *_chatWidget);
-    ~SplitHeader();
+    virtual ~SplitHeader();
 
     // Update channel text from chat widget
     void updateChannelText();