Fix T93500: Sequence.fps returns 0 when proxy is used

Caused by `seq_open_anim_file` early returning if anim struct exists,
exen if it's not initialized. To ensure `anim` struct is initialized
when `openfile` argument is true, don't do early return.

source/blender/sequencer/intern/utils.c

@@ -217,7 +217,7 @@ void seq_open_anim_file(Scene *scene, Sequence *seq, bool openfile)
   const bool is_multiview = (seq->flag & SEQ_USE_VIEWS) != 0 &&
                             (scene->r.scemode & R_MULTIVIEW) != 0;
 
-  if ((seq->anims.first != NULL) && (((StripAnim *)seq->anims.first)->anim != NULL)) {
+  if ((seq->anims.first != NULL) && (((StripAnim *)seq->anims.first)->anim != NULL) && !openfile) {
     return;
   }