Use 0/nullptr to indicate invalid Windows event handle in QLocalServer

The CreateEvent function returns NULL/nullptr if it failed, not
INVALID_HANDLE_VALUE(-1).

Change-Id: I7fb94061f4e14c014bf63acb53d3eee8f295eb66
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/network/socket/qlocalserver.cpp

@@ -197,7 +197,7 @@ qintptr QLocalServer::socketDescriptor() const
     return d->tcpServer.socketDescriptor();
 #elif defined(Q_OS_WIN)
     const auto handle = d->connectionEventNotifier->handle();
-    return handle != INVALID_HANDLE_VALUE ? qintptr(handle) : -1;
+    return handle ? qintptr(handle) : -1;
 #else
     return d->socketNotifier->socket();
 #endif

src/network/socket/qlocalserver_p.h

@@ -76,7 +76,7 @@ public:
     bool addListener();
 
     std::vector<std::unique_ptr<Listener>> listeners;
-    HANDLE eventHandle;
+    HANDLE eventHandle = nullptr;
     QWinEventNotifier *connectionEventNotifier;
 #else
     void setError(const QString &function);

src/network/socket/qlocalserver_win.cpp

@@ -215,7 +215,7 @@ bool QLocalServerPrivate::listen(const QString &name)
     // Use only one event for all listeners of one socket.
     // The idea is that listener events are rare, so polling all listeners once in a while is
     // cheap compared to waiting for N additional events in each iteration of the main loop.
-    eventHandle = CreateEvent(NULL, TRUE, FALSE, NULL);
+    eventHandle = CreateEvent(NULL, TRUE, FALSE, NULL); // If the function fails, the return value is NULL
     connectionEventNotifier = new QWinEventNotifier(eventHandle , q);
     q->connect(connectionEventNotifier, SIGNAL(activated(HANDLE)), q, SLOT(_q_onNewConnection()));
 
@@ -282,6 +282,7 @@ void QLocalServerPrivate::closeServer()
     connectionEventNotifier->deleteLater();
     connectionEventNotifier = 0;
     CloseHandle(eventHandle);
+    eventHandle = nullptr;
     for (size_t i = 0; i < listeners.size(); ++i)
         CloseHandle(listeners[i]->handle);
     listeners.clear();