Fix #122401: Missing animation rendering scene with "Render Single Layer"

Ensure that the re->r.scemode has R_SINGLE_LAYER when not rendering the
single layer.

Pull Request: https://projects.blender.org/blender/blender/pulls/122402

source/blender/render/intern/pipeline.cc

@@ -834,6 +834,9 @@ void RE_InitState(Render *re,
     STRNCPY(re->single_view_layer, single_layer->name);
     re->r.scemode |= R_SINGLE_LAYER;
   }
+  else {
+    re->r.scemode &= ~R_SINGLE_LAYER;
+  }
 
   /* if preview render, we try to keep old result */
   BLI_rw_mutex_lock(&re->resultmutex, THREAD_LOCK_WRITE);