source/blender/blenkernel/BKE_blender_version.h

@@ -29,7 +29,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 22
+#define BLENDER_FILE_SUBVERSION 23
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and cancel loading the file, showing a warning to

source/blender/blenkernel/BKE_nla.h

@@ -395,6 +395,12 @@ struct NlaStrip *BKE_nlastrip_find_active(struct NlaTrack *nlt);
  * Make the given NLA-Strip the active one within the given block.
  */
 void BKE_nlastrip_set_active(struct AnimData *adt, struct NlaStrip *strip);
+/**
+ * Find the NLA-strip with the given name within the given track.
+ *
+ * \return pointer to the strip, or nullptr when not found.
+ */
+struct NlaStrip *BKE_nlastrip_find_by_name(struct NlaTrack *nlt, const char *name);
 
 /**
  * Does the given NLA-strip fall within the given bounds (times)?.

source/blender/blenkernel/intern/nla.cc

@@ -1457,6 +1457,31 @@ void BKE_nlastrip_set_active(AnimData *adt, NlaStrip *strip)
   }
 }
 
+static NlaStrip *nlastrip_find_by_name(ListBase /* NlaStrip */ *strips, const char *name)
+{
+  LISTBASE_FOREACH (NlaStrip *, strip, strips) {
+    if (STREQ(strip->name, name)) {
+      return strip;
+    }
+
+    if (strip->type != NLASTRIP_TYPE_META) {
+      continue;
+    }
+
+    NlaStrip *inner_strip = nlastrip_find_by_name(&strip->strips, name);
+    if (inner_strip != nullptr) {
+      return inner_strip;
+    }
+  }
+
+  return nullptr;
+}
+
+NlaStrip *BKE_nlastrip_find_by_name(NlaTrack *nlt, const char *name)
+{
+  return nlastrip_find_by_name(&nlt->strips, name);
+}
+
 bool BKE_nlastrip_within_bounds(NlaStrip *strip, float min, float max)
 {
   const float stripLen = (strip) ? strip->end - strip->start : 0.0f;

source/blender/blenloader/intern/versioning_400.cc

@@ -16,6 +16,7 @@
 /* Define macros in `DNA_genfile.h`. */
 #define DNA_GENFILE_VERSIONING_MACROS
 
+#include "DNA_anim_types.h"
 #include "DNA_brush_types.h"
 #include "DNA_camera_types.h"
 #include "DNA_curve_types.h"
@@ -57,6 +58,7 @@
 #include "BKE_main.hh"
 #include "BKE_material.h"
 #include "BKE_mesh_legacy_convert.hh"
+#include "BKE_nla.h"
 #include "BKE_node.hh"
 #include "BKE_node_runtime.hh"
 #include "BKE_scene.h"
@@ -356,6 +358,51 @@ static void versioning_replace_splitviewer(bNodeTree *ntree)
   }
 }
 
+/**
+ * Exit NLA tweakmode when the AnimData struct has insufficient information.
+ *
+ * When NLA tweakmode is enabled, Blender expects certain pointers to be set up
+ * correctly, and if that fails, can crash. This function ensures that
+ * everything is consistent, by exiting tweakmode everywhere there's missing
+ * pointers.
+ *
+ * This shouldn't happen, but the example blend file attached to #119615 needs
+ * this.
+ */
+static void version_nla_tweakmode_incomplete(Main *bmain)
+{
+  bool any_valid_tweakmode_left = false;
+
+  ID *id;
+  FOREACH_MAIN_ID_BEGIN (bmain, id) {
+    AnimData *adt = BKE_animdata_from_id(id);
+    if (!adt || !(adt->flag & ADT_NLA_EDIT_ON)) {
+      continue;
+    }
+
+    if (adt->act_track && adt->actstrip) {
+      /* Expected case. */
+      any_valid_tweakmode_left = true;
+      continue;
+    }
+
+    /* Not enough info in the blend file to reliably stay in tweak mode. This is the most important
+     * part of this versioning code, as it prevents future nullptr access. */
+    BKE_nla_tweakmode_exit(adt);
+  }
+  FOREACH_MAIN_ID_END;
+
+  if (any_valid_tweakmode_left) {
+    /* There are still NLA strips correctly in tweak mode. */
+    return;
+  }
+
+  /* Nothing is in a valid tweakmode, so just disable the corresponding flags on all scenes. */
+  LISTBASE_FOREACH (Scene *, scene, &bmain->scenes) {
+    scene->flag &= ~SCE_NLA_EDIT_ON;
+  }
+}
+
 void do_versions_after_linking_400(FileData *fd, Main *bmain)
 {
   if (!MAIN_VERSION_FILE_ATLEAST(bmain, 400, 9)) {
@@ -450,6 +497,10 @@ void do_versions_after_linking_400(FileData *fd, Main *bmain)
     }
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 401, 23)) {
+    version_nla_tweakmode_incomplete(bmain);
+  }
+
   /**
    * Always bump subversion in BKE_blender_version.h when adding versioning
    * code here, and wrap it inside a MAIN_VERSION_FILE_ATLEAST check.

source/blender/makesrna/intern/rna_animation.cc

@@ -12,6 +12,7 @@
 #include "DNA_anim_types.h"
 #include "DNA_scene_types.h"
 
+#include "BLI_listbase_wrapper.hh"
 #include "BLI_utildefines.h"
 
 #include "BLT_translation.h"
@@ -189,6 +190,34 @@ bool rna_AnimData_tweakmode_override_apply(Main * /*bmain*/,
 
   anim_data_dst->flag = (anim_data_dst->flag & ~ADT_NLA_EDIT_ON) |
                         (anim_data_src->flag & ADT_NLA_EDIT_ON);
+
+  if (!(anim_data_dst->flag & ADT_NLA_EDIT_ON)) {
+    /* If tweak mode is not enabled, there's nothing left to do. */
+    return true;
+  }
+
+  if (!anim_data_src->act_track || !anim_data_src->actstrip) {
+    /* If there is not enough information to find the active track/strip, don't bother. */
+    return true;
+  }
+
+  /* AnimData::act_track and AnimData::actstrip are not directly exposed to RNA as editable &
+   * overridable, so the override doesn't contain this info. Reconstruct the pointers by name. */
+  for (NlaTrack *track : blender::ListBaseWrapper<NlaTrack>(anim_data_dst->nla_tracks)) {
+    if (!STREQ(track->name, anim_data_src->act_track->name)) {
+      continue;
+    }
+
+    NlaStrip *strip = BKE_nlastrip_find_by_name(track, anim_data_src->actstrip->name);
+    if (!strip) {
+      continue;
+    }
+
+    anim_data_dst->act_track = track;
+    anim_data_dst->actstrip = strip;
+    break;
+  }
+
   return true;
 }