Erwan - cache fixes - Code review highly appreciated, please criticize my code!

- fix issue 65 (quads when no image  load slowly in shop/deck editor)
- Possibly fix issue 92, please let me know if it reproduces
- Fix issue 97 (Deck editor: weird behavior of deck display)
- Fix issue 39 - please verify
- Issue 56 can probably be closed as well
- Fix issue 86

projects/mtg/src/GuiCombat.cpp

@@ -28,8 +28,10 @@ GuiCombat::GuiCombat(GameObserver* go) : GuiLayer(), go(go), active(false), acti
 
 GuiCombat::~GuiCombat()
 {
-  if(ok_tex)
+  if(ok_tex){
     resources.Release(ok_tex);
+    ok_tex = NULL;
+  }
 
   for (inner_iterator it = attackers.begin(); it != attackers.end(); ++it)
     {