The big NULL replacement party part 1.

This is meant to be a safer alternative since
NULL can often be 0. Let's not rely on that.

And yes, I know this is a lot of files. This is
a safer thing to do in big commits vs for loops.

src/ScreenMiniMenu.cpp

@@ -59,7 +59,7 @@ void ScreenMiniMenu::Init()
 
 void ScreenMiniMenu::BeginScreen()
 {
-	ASSERT( g_pMenuDef != NULL );
+	ASSERT( g_pMenuDef != nullptr );
 
 	LoadMenu( g_pMenuDef );
 	m_SMSendOnOK = g_SendOnOK;