Linux device fix by zeitgeisty.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@729 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/CIrrDeviceLinux.h

@@ -99,7 +99,7 @@ namespace irr
 				: Device(dev), IsVisible(true), Null(null), UseReferenceRect(false)
 			{
 #ifdef _IRR_COMPILE_WITH_X11_
-				if (!null)
+				if (!Null)
 				{
 					XGCValues values;
 					unsigned long valuemask = 0;
@@ -133,6 +133,7 @@ namespace irr
 			~CCursorControl()
 			{
 #ifdef _IRR_COMPILE_WITH_X11_
+				if (!Null)
 					XFreeGC(Device->display, gc);
 #endif
 			}