message: Fix build on native MacOSX
  * Fix build on native MacOSX
  In cbc2e5 a bug got introduced while trying to special cases
  for Qt >= 5.2
  * Use c++11 nullptr literal
diff: #include <objc/objc.h>
  #include <objc/message.h>
  -static MacDockIconHandler *s_instance = NULL;
  +static MacDockIconHandler *s_instance = nullptr;
  bool dockClickHandler(id self,SEL _cmd,...) {
  Q_UNUSED(self)
  @@ -31,7 +31,7 @@ void setupDockClickHandler() {
  Class cls = objc_getClass("NSApplication");
  id appInst = objc_msgSend((id)cls, sel_registerName("sharedApplication"));
  - if (appInst != NULL) {
  + if (appInst != nullptr) {
  id delegate = objc_msgSend(appInst, sel_registerName("delegate"));
  Class delClass = (Class)objc_msgSend(delegate, sel_registerName("class"));
  SEL shouldHandle = sel_registerName("applicationShouldHandleReopen:hasVisibleWindows:");
  @@ -50,8 +50,8 @@ MacDockIconHandler::MacDockIconHandler() : QObject()
  setupDockClickHandler();
  this->m_dummyWidget = new QWidget();
  this->m_dockMenu = new QMenu(this->m_dummyWidget);
  - this->setMainWindow(NULL);
  -#elif QT_VERSION >= 0x050200
  + this->setMainWindow(nullptr);
  +#if QT_VERSION >= 0x050200
  this->m_dockMenu->setAsDockMenu();
  #endif
  [pool release];
  @@ -64,7 +64,7 @@ void MacDockIconHandler::setMainWindow(QMainWindow *window) {
  MacDockIconHandler::~MacDockIconHandler()
  {
  delete this->m_dummyWidget;
  - this->setMainWindow(NULL);
  + this->setMainWindow(nullptr);
  }
  QMenu *MacDockIconHandler::dockMenu()
  