test(auth): add regression tests for JWTHandler.is_jwt(None)

Add None-token test cases to both proxy_unit_tests and test_litellm
to cover the guard added in the previous commit. Also add -> bool
return type annotation to is_jwt().

litellm/proxy/auth/handle_jwt.py

@@ -89,7 +89,7 @@ class JWTHandler:
         self.leeway = leeway
 
     @staticmethod
-    def is_jwt(token: Optional[str]):
+    def is_jwt(token: Optional[str]) -> bool:
         if token is None:
             return False
         parts = token.split(".")

tests/proxy_unit_tests/test_jwt.py

@@ -1331,6 +1331,9 @@ def test_jwt_handler_is_jwt_static_method():
     # Test with empty string
     assert JWTHandler.is_jwt("") == False
 
+    # Test with None (missing Authorization header)
+    assert JWTHandler.is_jwt(None) == False
+
 
 @pytest.mark.parametrize(
     "requested_model, should_work",

tests/test_litellm/proxy/auth/test_user_api_key_auth.py

@@ -567,6 +567,10 @@ class TestJWTOAuth2Coexistence:
         assert JWTHandler.is_jwt("Bearer token") is False
         assert JWTHandler.is_jwt("two.parts") is False
 
+    def test_is_jwt_returns_false_for_none(self):
+        """None token (missing Authorization header) should not be treated as JWT."""
+        assert JWTHandler.is_jwt(None) is False
+
     @pytest.mark.asyncio
     async def test_both_enabled_opaque_token_uses_oauth2(self):
         """