Don't take editor input when fading out

This fixes being able to re-trigger the fadeout while a fadeout is
already happening. It also fixes being able to enter playtesting during
the fadeout, which means the level now has a fadeout you normally can't
do in actual gameplay.

desktop_version/src/editor.cpp

@@ -3974,6 +3974,10 @@ static void editormenuactionpress(void)
 void editorinput(void)
 {
     extern editorclass ed;
+    if (graphics.fademode == 3 /* fading out */)
+    {
+        return;
+    }
     game.mx = (float) key.mx;
     game.my = (float) key.my;
     ed.tilex=(game.mx - (game.mx%8))/8;