Fix #146529: Crash getting RNA path to scene rigid body pointcache

Spawning the tooltip or changing values would cause this.

Error in 28827b62f7

Above commit only considered PointCaches associated with **objects**,
not taking into account scene rigid body cache.
This is now added with this PR.
Previously it would cast into modifiers when we actually had a scene as
owner... resulting in a crash.

This was only exposed by 6bf8685628 (it crashes since, was just not
working properly before...). 6bf8685628 changed the data layout of
`struct Object` and only by pure luck the modifiers loop was skipped, now
with the new layout it is entered (but with garbage data resulting in the crash.

Pull Request: https://projects.blender.org/blender/blender/pulls/146577

source/blender/makesrna/intern/rna_object_force.cc

@@ -118,7 +118,7 @@ static const EnumPropertyItem empty_vortex_shape_items[] = {
 
 #  include "ED_object.hh"
 
-static bool rna_Cache_get_valid_owner_ID(PointerRNA *ptr, Object **ob, Scene **scene)
+static bool rna_Cache_get_valid_owner_ID(const PointerRNA *ptr, Object **ob, Scene **scene)
 {
   switch (GS(ptr->owner_id->name)) {
     case ID_OB:
@@ -139,10 +139,27 @@ static bool rna_Cache_get_valid_owner_ID(PointerRNA *ptr, Object **ob, Scene **s
 
 static std::optional<std::string> rna_PointCache_path(const PointerRNA *ptr)
 {
-  ModifierData *md;
-  Object *ob = (Object *)ptr->owner_id;
   PointCache *cache = static_cast<PointCache *>(ptr->data);
 
+  Object *ob = nullptr;
+  Scene *scene = nullptr;
+
+  if (!rna_Cache_get_valid_owner_ID(ptr, &ob, &scene)) {
+    return std::nullopt;
+  }
+
+  /* Scene rigid body. */
+  if (scene != nullptr && scene->rigidbody_world->shared != nullptr) {
+    if (scene->rigidbody_world->shared->pointcache == cache) {
+      return "rigidbody_world.point_cache";
+    }
+  }
+
+  if (!ob) {
+    return std::nullopt;
+  }
+
+  ModifierData *md;
   for (md = static_cast<ModifierData *>(ob->modifiers.first); md; md = md->next) {
     const ModifierTypeInfo *mti = BKE_modifier_get_info(ModifierType(md->type));
 
@@ -198,6 +215,7 @@ static std::optional<std::string> rna_PointCache_path(const PointerRNA *ptr)
       }
     }
   }
+
   return std::nullopt;
 }