Add pointer-check for cursor before update to avoid crash when window generation failed.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@3758 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/CIrrDeviceLinux.cpp

@@ -843,7 +843,8 @@ bool CIrrDeviceLinux::run()
 
 #ifdef _IRR_COMPILE_WITH_X11_
 
-	static_cast<CCursorControl*>(CursorControl)->update();
+	if ( CursorControl )
+		static_cast<CCursorControl*>(CursorControl)->update();
 
 	if ((CreationParams.DriverType != video::EDT_NULL) && display)
 	{