fix: offline model retrieval, re-raise to disable instead of returning useless fallback (#22106)

Co-authored-by: ahxxm <1286225+ahxxm@users.noreply.github.com>

backend/open_webui/retrieval/utils.py

@@ -1306,6 +1306,8 @@ def get_model_path(model: str, update_model: bool = False):
         return model_repo_path
     except Exception as e:
         log.exception(f"Cannot determine model snapshot path: {e}")
+        if OFFLINE_MODE:
+            raise
         return model