fix: GUI Disappearing #1522 (Mac OSX)

- this solution works stable on mac and ensures that the window get's reopened when the user clicks the dock icon .
- tested on 10.8 with Qt4.8.4 and Qt5.0.1

Signed-off-by: Jonas Schnelli <jonas.schnelli@include7.ch>

src/qt/macdockiconhandler.mm

@@ -37,8 +37,9 @@ extern void qt_mac_set_dock_menu(QMenu*);
     Q_UNUSED(event)
     Q_UNUSED(replyEvent)
 
-    if (dockIconHandler)
+    if (dockIconHandler) {
         dockIconHandler->handleDockIconClickEvent();
+    }
 }
 
 @end
@@ -54,10 +55,15 @@ MacDockIconHandler::MacDockIconHandler() : QObject()
     [pool release];
 }
 
+void MacDockIconHandler::setMainWindow(QMainWindow *window) {
+    this->mainWindow = window;
+}
+
 MacDockIconHandler::~MacDockIconHandler()
 {
     [this->m_dockIconClickEventHandler release];
     delete this->m_dummyWidget;
+    this->setMainWindow(NULL);
 }
 
 QMenu *MacDockIconHandler::dockMenu()
@@ -94,5 +100,8 @@ MacDockIconHandler *MacDockIconHandler::instance()
 
 void MacDockIconHandler::handleDockIconClickEvent()
 {
+    this->mainWindow->activateWindow();
+    this->mainWindow->show();
+
     emit this->dockIconClicked();
 }