Fix T103601: Crash on making Contactsheet

Python API for moving strips to and from meta strips did not invalidate
strip lookup cache. Because of that, `SEQ_get_seqbase_by_seq()` failed
to lookup origin of strip, which resulted in crash on NULL dereference.

Invalidateion was added to functions `SEQ_edit_move_strip_to_meta()` and
`SEQ_add_meta_strip()`.

source/blender/makesrna/intern/rna_sequencer_api.c

@@ -22,7 +22,7 @@
 
 #ifdef RNA_RUNTIME
 
-//#include "DNA_anim_types.h"
+// #include "DNA_anim_types.h"
 #  include "DNA_image_types.h"
 #  include "DNA_mask_types.h"
 #  include "DNA_sound_types.h"
@@ -83,6 +83,8 @@ static void rna_Sequences_move_strip_to_meta(
   DEG_relations_tag_update(bmain);
   DEG_id_tag_update(&scene->id, ID_RECALC_SEQUENCER_STRIPS);
 
+  SEQ_sequence_lookup_tag(scene, SEQ_LOOKUP_TAG_INVALID);
+
   WM_main_add_notifier(NC_SCENE | ND_SEQUENCER, scene);
 }
 

source/blender/sequencer/intern/strip_add.c

@@ -367,6 +367,8 @@ Sequence *SEQ_add_meta_strip(Scene *scene, ListBase *seqbase, SeqLoadData *load_
   seqm->start = load_data->start_frame;
   seqm->len = 1;
 
+  seq_add_generic_update(scene, seqm);
+
   return seqm;
 }