EEVEE Next: Fix crash on Scenes without a World

Create a default world when scenes don't have one.
This is a 1:1 copy of the current EEVEE implementation.

Pull Request: https://projects.blender.org/blender/blender/pulls/107891

source/blender/draw/engines/eevee_next/eevee_world.cc

@@ -57,6 +57,23 @@ bNodeTree *DefaultWorldNodeTree::nodetree_get(::World *wo)
  *
  * \{ */
 
+World::~World()
+{
+  BKE_id_free(nullptr, default_world_);
+}
+
+::World *World::default_world_get()
+{
+  if (default_world_ == nullptr) {
+    default_world_ = static_cast<::World *>(BKE_id_new_nomain(ID_WO, "EEVEEE default world"));
+    copy_v3_fl(&default_world_->horr, 0.0f);
+    default_world_->use_nodes = 0;
+    default_world_->nodetree = nullptr;
+    BLI_listbase_clear(&default_world_->gpumaterial);
+  }
+  return default_world_;
+}
+
 void World::sync()
 {
   // if (inst_.lookdev.sync_world()) {
@@ -65,8 +82,7 @@ void World::sync()
 
   ::World *bl_world = inst_.scene->world;
   if (bl_world == nullptr) {
-    // bl_world = BKE_world_default();
-    return;
+    bl_world = default_world_get();
   }
 
   WorldHandle &wo_handle = inst_.sync.sync_world(bl_world);

source/blender/draw/engines/eevee_next/eevee_world.hh

@@ -53,8 +53,13 @@ class World {
   /* Used to detect if world change. */
   ::World *prev_original_world = nullptr;
 
+  /* Used when the scene doesn't have a world. */
+  ::World *default_world_ = nullptr;
+  ::World *default_world_get();
+
  public:
   World(Instance &inst) : inst_(inst){};
+  ~World();
 
   void sync();
 };