fix: regenerate the truth before a native refresh

scripts/export_native.py

@@ -265,8 +265,11 @@ class StaleTruth(ValueError):
 @functools.lru_cache(maxsize=None)
 def _truth_sources(platforms_dir: str) -> tuple[dict, dict, dict | None]:
     """Registry, profiles and database, as generate_truth reads them."""
-    with open(Path(platforms_dir) / "_registry.yml") as handle:
-        registry = (yaml_load(handle) or {}).get("platforms", {})
+    registry_path = Path(platforms_dir) / "_registry.yml"
+    registry: dict = {}
+    if registry_path.exists():
+        with open(registry_path) as handle:
+            registry = (yaml_load(handle) or {}).get("platforms", {})
     profiles = load_emulator_profiles("emulators")
     db = load_database(TRUTH_DB) if Path(TRUTH_DB).exists() else None
     return registry, profiles, db