[CsMain] Fix for small bug with new event system

[Mathew Sutcliffe]

While working on my uni project, I found a small bug in the engine 
plugin, that was introduced with the new event system. 
csEngine::Initialize() will segfault on line 815 of 
plugins/engine/3d/engine.cpp by referencing a null pointer, if either of 
the iGraphics2D or 3D plugins is not available. The engine is still 
supposed to be able to function without those plugins.

The fix is quite trivial. Attached is a patch, as I lost my CVS write 
access during the spring clean. You might want to apply the patch or you 
might want to just do it yourself if you want to fix it in a different way.
diff -c -3 -r1.106 engine.cpp
*** plugins/engine/3d/engine.cpp        8 Dec 2005 07:30:47 -0000       1.106
--- plugins/engine/3d/engine.cpp        15 Dec 2005 17:22:54 -0000
***************
*** 812,819 ****
  
    // Tell event queue that we want to handle broadcast events
    CS_INITIALIZE_SYSTEM_EVENT_SHORTCUTS(objectRegistry);
!   CanvasResize = csevCanvasResize (objectRegistry, G2D);
!   CanvasClose = csevCanvasClose (objectRegistry, G2D);
  
    csRef<iEventQueue> q = CS_QUERY_REGISTRY (objectRegistry, iEventQueue);
    if (q)
--- 812,822 ----
  
    // Tell event queue that we want to handle broadcast events
    CS_INITIALIZE_SYSTEM_EVENT_SHORTCUTS(objectRegistry);
!   if (G2D)
!   {
!     CanvasResize = csevCanvasResize (objectRegistry, G2D);
!     CanvasClose = csevCanvasClose (objectRegistry, G2D);
!   }
  
    csRef<iEventQueue> q = CS_QUERY_REGISTRY (objectRegistry, iEventQueue);
    if (q)
***************
*** 821,826 ****
--- 824,833 ----
      csEventID events[5] = { SystemOpen, SystemClose,
                            CanvasResize, CanvasClose,
                            CS_EVENTLIST_END };
+ 
+     // discard canvas events if there is no canvas, by truncating the array
+     if (!G2D) events[2] = CS_EVENTLIST_END;
+ 
      q->RegisterListener (scfiEventHandler, events);
    }