TQDesktopWidget: Fix SIGSEGV in case class is accessed before init()

If screenCount/rects get accessed before init() it may result in
SIGSEGV. Namely in TQDesktopWidget::resizeEvent() after recent changes.

Signed-off-by: Alexander Golubev <fatzer2@gmail.com>

src/kernel/tqdesktopwidget_x11.cpp

@@ -94,7 +94,7 @@ public:
 };
 
 TQDesktopWidgetPrivate::TQDesktopWidgetPrivate()
-    : use_xinerama(false), defaultScreen(0), screenCount(1),
+    : use_xinerama(false), defaultScreen(0), screenCount(0),
       screens( 0 ), rects( 0 ), workareas( 0 )
 {
 }