Added safety harness for currentThreadObject() usage.

currentThreadObject() returns a null pointer if the
current thread was not started using the QThread API.
This relates to bug 1748.

(cherry picked from commit dad70b4c52)
Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>

src/kernel/qeventloop_unix_glib.cpp

@@ -688,7 +688,9 @@ int QEventLoop::activateTimers()
 		QTimerEvent e( t->id );
 #if defined(QT_THREAD_SUPPORT)
 		// Be careful...the current thread may not be the target object's thread!
-		if ((!t->obj) || (QThread::currentThreadObject()->threadPostedEventsDisabled()) || (t->obj && (t->obj->contextThreadObject() == QThread::currentThreadObject()))) {
+		if ((!t->obj) || 
+		    (QThread::currentThreadObject() && QThread::currentThreadObject()->threadPostedEventsDisabled()) ||
+		    (t->obj && t->obj->contextThreadObject() == QThread::currentThreadObject())) {
 			QApplication::sendEvent( t->obj, &e );				// send event
 		}
 		else {
@@ -731,7 +733,9 @@ int QEventLoop::activateSocketNotifiers()
 		sn->pending = FALSE;
 #if defined(QT_THREAD_SUPPORT)
 		// Be careful...the current thread may not be the target object's thread!
-		if ((!sn->obj) || (QThread::currentThreadObject()->threadPostedEventsDisabled()) || (sn->obj && (sn->obj->contextThreadObject() == QThread::currentThreadObject()))) {
+		if ((!sn->obj) || 
+		    (QThread::currentThreadObject() && QThread::currentThreadObject()->threadPostedEventsDisabled()) ||
+		    (sn->obj && sn->obj->contextThreadObject() == QThread::currentThreadObject())) {
 			QApplication::sendEvent( sn->obj, &event );			// send event
 		}
 		else {

src/kernel/qobject.cpp

@@ -203,9 +203,10 @@ void QObject::moveToThread(QThread *targetThread)
     }
 
     QThread *objectThread = contextThreadObject();
+    // NOTE currentThread could be NULL if the current thread was not started using the QThread API
     QThread *currentThread = QThread::currentThreadObject();
 
-    if (objectThread != currentThread) {
+    if (currentThread && objectThread != currentThread) {
 #if defined(QT_DEBUG)
         qWarning( "QObject::moveToThread: Current thread is not the object's thread" );
 #endif
@@ -2760,6 +2761,7 @@ void QObject::activate_signal( QConnectionList *clist, QUObject *o )
     }
 #endif
 
+    // NOTE currentThread could be NULL if the current thread was not started using the QThread API
     const QThread *currentThread = QThread::currentThreadObject();
 
     QObject *object;
@@ -2779,7 +2781,10 @@ void QObject::activate_signal( QConnectionList *clist, QUObject *o )
 	    sol->currentSender = this;
 	}
 	if ( c->memberType() == QSIGNAL_CODE ) {
-	    if ((d->disableThreadPostedEvents) || (object->d->disableThreadPostedEvents) || (currentThread->threadPostedEventsDisabled()) || (object->d->ownThread == currentThread)) {
+	    if ((d->disableThreadPostedEvents) || 
+	        (object->d->disableThreadPostedEvents) || 
+	        (currentThread && currentThread->threadPostedEventsDisabled()) || 
+	        (currentThread && object->d->ownThread == currentThread)) {
 #ifdef QT_THREAD_SUPPORT
 		sol->listMutex->unlock();
 #endif // QT_THREAD_SUPPORT
@@ -2798,7 +2803,10 @@ void QObject::activate_signal( QConnectionList *clist, QUObject *o )
 	    }
 	}
 	else {
-	    if ((d->disableThreadPostedEvents) || (object->d->disableThreadPostedEvents) || (currentThread->threadPostedEventsDisabled()) || (object->d->ownThread == currentThread)) {
+	    if ((d->disableThreadPostedEvents) || 
+	        (object->d->disableThreadPostedEvents) || 
+	        (currentThread && currentThread->threadPostedEventsDisabled()) || 
+	        (currentThread && object->d->ownThread == currentThread)) {
 #ifdef QT_THREAD_SUPPORT
 		sol->listMutex->unlock();
 #endif // QT_THREAD_SUPPORT
@@ -2846,7 +2854,10 @@ void QObject::activate_signal( QConnectionList *clist, QUObject *o )
 		sol->currentSender = this;
 	    }
 	    if ( c->memberType() == QSIGNAL_CODE ) {
-		if ((d->disableThreadPostedEvents) || (object->d->disableThreadPostedEvents) || (currentThread->threadPostedEventsDisabled()) || (object->d->ownThread == currentThread)) {
+		if ((d->disableThreadPostedEvents) || 
+		    (object->d->disableThreadPostedEvents) || 
+		    (currentThread && currentThread->threadPostedEventsDisabled()) || 
+		    (currentThread && object->d->ownThread == currentThread)) {
 #ifdef QT_THREAD_SUPPORT
 		    sol->listMutex->unlock();
 #endif // QT_THREAD_SUPPORT
@@ -2865,7 +2876,10 @@ void QObject::activate_signal( QConnectionList *clist, QUObject *o )
 		}
 	    }
 	    else {
-		if ((d->disableThreadPostedEvents) || (object->d->disableThreadPostedEvents) || (currentThread->threadPostedEventsDisabled()) || (object->d->ownThread == currentThread)) {
+		if ((d->disableThreadPostedEvents) || 
+		    (object->d->disableThreadPostedEvents) || 
+		    (currentThread && currentThread->threadPostedEventsDisabled()) || 
+		    (currentThread && object->d->ownThread == currentThread)) {
 #ifdef QT_THREAD_SUPPORT
 		    sol->listMutex->unlock();
 #endif // QT_THREAD_SUPPORT