Fix T98021: Crash when using scene strip as sequencer input

Issue was caused by treating such strip as meta and using
`seq->channels` directly, which is not valid for scene strips.

Pointer to channels is now provided by function
`SEQ_get_seqbase_from_sequence`.

3 files changed, 8 insertions, 4 deletions

diff --git a/source/blender/sequencer/SEQ_utils.h b/source/blender/sequencer/SEQ_utils.h
index ec33bca87a3..ce3c81606ea 100644
--- a/source/blender/sequencer/SEQ_utils.h
+++ b/source/blender/sequencer/SEQ_utils.h
@@ -32,7 +32,9 @@ void SEQ_sequence_base_unique_name_recursive(struct Scene *scene,
                                              struct ListBase *seqbasep,
                                              struct Sequence *seq);
 const char *SEQ_sequence_give_name(struct Sequence *seq);
-struct ListBase *SEQ_get_seqbase_from_sequence(struct Sequence *seq, int *r_offset);
+struct ListBase *SEQ_get_seqbase_from_sequence(struct Sequence *seq,
+                                               struct ListBase **channels,
+                                               int *r_offset);
 const struct Sequence *SEQ_get_topmost_sequence(const struct Scene *scene, int frame);
 /**
  * In cases where we don't know the sequence's listbase.
diff --git a/source/blender/sequencer/intern/render.c b/source/blender/sequencer/intern/render.c
index 8d8a13be09e..1b9e89a35d5 100644
--- a/source/blender/sequencer/intern/render.c
+++ b/source/blender/sequencer/intern/render.c
@@ -1586,10 +1586,10 @@ static ImBuf *do_render_strip_seqbase(const SeqRenderData *context,
 {
   ImBuf *ibuf = NULL;
   ListBase *seqbase = NULL;
-  ListBase *channels = &seq->channels;
+  ListBase *channels = NULL;
   int offset;
 
-  seqbase = SEQ_get_seqbase_from_sequence(seq, &offset);
+  seqbase = SEQ_get_seqbase_from_sequence(seq, &channels, &offset);
 
   if (seqbase && !BLI_listbase_is_empty(seqbase)) {
 
diff --git a/source/blender/sequencer/intern/utils.c b/source/blender/sequencer/intern/utils.c
index da422c4228f..0cf47420d8f 100644
--- a/source/blender/sequencer/intern/utils.c
+++ b/source/blender/sequencer/intern/utils.c
@@ -225,13 +225,14 @@ const char *SEQ_sequence_give_name(Sequence *seq)
   return name;
 }
 
-ListBase *SEQ_get_seqbase_from_sequence(Sequence *seq, int *r_offset)
+ListBase *SEQ_get_seqbase_from_sequence(Sequence *seq, ListBase **r_channels, int *r_offset)
 {
   ListBase *seqbase = NULL;
 
   switch (seq->type) {
     case SEQ_TYPE_META: {
       seqbase = &seq->seqbase;
+      *r_channels = &seq->channels;
       *r_offset = seq->start;
       break;
     }
@@ -240,6 +241,7 @@ ListBase *SEQ_get_seqbase_from_sequence(Sequence *seq, int *r_offset)
         Editing *ed = SEQ_editing_get(seq->scene);
         if (ed) {
           seqbase = &ed->seqbase;
+          *r_channels = &ed->channels;
           *r_offset = seq->scene->r.sfra;
         }
       }