Fix #118213: Applying effects to VSE Color/Text strips makes both the effect and source strip visible

This is different from applying effects to regular "source media" strips
like images or movies; an effect "hides" the input strip when it is
below itself in the channel.

Apply the same treatment to Color & Text strips. Fixes #118213.

If someone wants previous behavior for some reason, they can drag
the effect applied on Color/Text to be below the input strip.

Pull Request: https://projects.blender.org/blender/blender/pulls/118269

source/blender/sequencer/intern/iterator.cc

@@ -1,5 +1,5 @@
 /* SPDX-FileCopyrightText: 2001-2002 NaN Holding BV. All rights reserved.
- * SPDX-FileCopyrightText: 2003-2009 Blender Authors
+ * SPDX-FileCopyrightText: 2003-2024 Blender Authors
  * SPDX-FileCopyrightText: 2005-2006 Peter Schlaile <peter [at] schlaile [dot] de>
  *
  * SPDX-License-Identifier: GPL-2.0-or-later */
@@ -21,6 +21,7 @@
 
 #include "BKE_scene.h"
 
+#include "SEQ_effects.hh"
 #include "SEQ_iterator.hh"
 #include "SEQ_relations.hh"
 #include "SEQ_render.hh"
@@ -178,8 +179,8 @@ static bool must_render_strip(VectorSet<Sequence *> &strips, Sequence *strip)
     }
   }
 
-  /* All effects are rendered (with respect to conditions above). */
-  if ((strip->type & SEQ_TYPE_EFFECT) != 0) {
+  /* All non-generator effects are rendered (with respect to conditions above). */
+  if ((strip->type & SEQ_TYPE_EFFECT) != 0 && SEQ_effect_get_num_inputs(strip->type) != 0) {
     return true;
   }