Display improper zip structure message to non-console users

If a zip file is improperly structured, a message will be displayed when
the player loads the level list.

This will only display the last-displayed improper zip, because there
only needs to be one displayed at a time. Also because doing anything
more would most likely require heap allocation, and I don't want to do
that.

desktop_version/src/Render.cpp

@@ -1391,6 +1391,10 @@ static void menurender(void)
         graphics.bigprint(-1, 45, "ERROR", tr, tg, tb, true);
         graphics.PrintWrap(-1, 65, graphics.error, tr, tg, tb, true, 10, 304);
         break;
+    case Menu::warninglevellist:
+        graphics.bigprint(-1, 45, "WARNING", tr, tg, tb, true);
+        graphics.PrintWrap(-1, 65, FILESYSTEM_getLevelDirError(), tr, tg, tb, true, 10, 304);
+        break;
     default:
         break;
     }