v3.11.11: fix UnboundLocalError last_role in Gemini sanitizer

src/translate-proxy.py

@@ -5574,6 +5574,7 @@ class Handler(http.server.BaseHTTPRequestHandler):
         if OAUTH_PROVIDER.startswith("google") and "claude" not in model.lower():
             sanitized = []
             last_user_text = None
+            last_role = None
             for content in contents:
                 role = content.get("role")
                 parts = [p for p in content.get("parts", []) if isinstance(p, dict)]