Ref T182, overlay messages can be closed + some fixes

* no slots needed
* check for nullptr
* init kill button correctly

src/blackgui/overlaymessages.cpp

@@ -302,6 +302,7 @@ namespace BlackGui
     void COverlayMessages::showKillButton(bool killButton)
     {
         m_hasKillButton = killButton;
+        this->showKill(killButton);
     }
 
     void COverlayMessages::setModeToMessages(bool withKillButton)

src/blackgui/overlaymessagesframe.cpp

@@ -21,6 +21,8 @@
 #include <Qt>
 #include <algorithm>
 
+using namespace BlackMisc;
+
 namespace BlackGui
 {
     COverlayMessagesFrame::COverlayMessagesFrame(QWidget *parent) :
@@ -59,10 +61,17 @@ namespace BlackGui
 
     void COverlayMessagesFrame::clearOverlayMessages()
     {
+        if (!m_overlayMessages) { return; }
         m_overlayMessages->clearOverlayMessages();
     }
 
-    void COverlayMessagesFrame::showOverlayMessage(const BlackMisc::CStatusMessage &message, int timeOutMs)
+    void COverlayMessagesFrame::closeOverlay()
+    {
+        if (!m_overlayMessages) { return; }
+        m_overlayMessages->close();
+    }
+
+    void COverlayMessagesFrame::showOverlayMessage(const CStatusMessage &message, int timeOutMs)
     {
         if (message.isEmpty()) { return; }
         this->initInnerFrame();

src/blackgui/overlaymessagesframe.h

@@ -65,10 +65,12 @@ namespace BlackGui
             int                                 timeOutMs = -1
         );
 
-        //! Clear the overlay messages
+        //! \copydoc COverlayMessages::clearOverlayMessages
         void clearOverlayMessages();
 
-    public slots:
+        //! \copydoc COverlayMessages::close
+        void closeOverlay();
+
         //! \copydoc COverlayMessages::showOverlayMessages
         void showOverlayMessages(const BlackMisc::CStatusMessageList &messages, bool appendOldMessages = false, int timeOutMs = -1);