Fix NO_CUSTOM_LEVELS compile after #158

ifdef out the code that draws the "return to editor" text in
NO_CUSTOM_LEVELS builds now that it accesses variables in the
editor class (PR #158)

desktop_version/src/titlerender.cpp

@@ -1604,6 +1604,7 @@ void gamerender(Graphics& dwgfx, mapclass& map, Game& game, entityclass& obj, Ut
         }
     }
 
+#if !defined(NO_CUSTOM_LEVELS)
      if(map.custommode && !map.custommodeforreal && !game.advancetext){
         //Return to level editor
         dwgfx.bprintalpha(5, 5, "[Press ENTER to return to editor]", 220 - (help.glow), 220 - (help.glow), 255 - (help.glow / 2), ed.returneditoralpha, false);
@@ -1611,6 +1612,7 @@ void gamerender(Graphics& dwgfx, mapclass& map, Game& game, entityclass& obj, Ut
             ed.returneditoralpha -= 15;
         }
       }
+#endif
 
 
     dwgfx.cutscenebars();