Fix: AssetShelfSettings memory management issues (assignment & destructor)

Rewrite `AssetShelfSettings::operator=` and fix `~AssetShelfSettings()`
to address some memory management issues:

- `memcpy` was used to copy a C++ struct, which shouldn't be done: it
  can cause undefined behaviour if the class has vtables or internal
  padding. This isn't the case here, but GCC nonetheless warns for it.
- `active_catalog_path` was incorrectly freed via `MEM_delete()`; it was
  allocated with `BLI_strdup()`, which uses `MEM_malloc_arrayN()` and
  thus should be freed with `MEM_freeN()`.
- Self-assignments weren't handled properly, and could cause data loss.

These are now all fixed.

Pull Request: https://projects.blender.org/blender/blender/pulls/143701

source/blender/editors/asset/intern/asset_shelf_settings.cc

@@ -17,6 +17,7 @@
 
 #include "BLI_listbase.h"
 #include "BLI_string.h"
+#include "BLI_string_utf8.h"
 
 #include "BKE_asset.hh"
 #include "BKE_preferences.h"
@@ -36,13 +37,24 @@ AssetShelfSettings::AssetShelfSettings(const AssetShelfSettings &other)
 
 AssetShelfSettings &AssetShelfSettings::operator=(const AssetShelfSettings &other)
 {
-  /* Start with a shallow copy. */
-  memcpy(this, &other, sizeof(AssetShelfSettings));
-
-  if (active_catalog_path) {
-    active_catalog_path = BLI_strdup(other.active_catalog_path);
+  if (this == &other) {
+    return *this; /* Handle self-assignment safely. */
   }
-  enabled_catalog_paths = BKE_asset_catalog_path_list_duplicate(other.enabled_catalog_paths);
+
+  /* Free existing properties. */
+  BKE_asset_catalog_path_list_free(this->enabled_catalog_paths);
+  MEM_SAFE_FREE(this->active_catalog_path);
+
+  /* Copy from 'other'. */
+  this->asset_library_reference = other.asset_library_reference;
+  STRNCPY_UTF8(this->search_string, other.search_string);
+  this->preview_size = other.preview_size;
+  this->display_flag = other.display_flag;
+
+  if (other.active_catalog_path) {
+    this->active_catalog_path = BLI_strdup(other.active_catalog_path);
+  }
+  this->enabled_catalog_paths = BKE_asset_catalog_path_list_duplicate(other.enabled_catalog_paths);
 
   return *this;
 }
@@ -50,7 +62,7 @@ AssetShelfSettings &AssetShelfSettings::operator=(const AssetShelfSettings &othe
 AssetShelfSettings::~AssetShelfSettings()
 {
   BKE_asset_catalog_path_list_free(enabled_catalog_paths);
-  MEM_delete(active_catalog_path);
+  MEM_SAFE_FREE(active_catalog_path);
 }
 
 namespace blender::ed::asset::shelf {