Check that expires_in is explicitly not None, can be 0

Author: keurcien

src/mcp/client/auth/oauth2.py

@@ -468,7 +468,7 @@ async def _initialize(self) -> None:  # pragma: no cover
         self.context.current_tokens = await self.context.storage.get_tokens()
         self.context.client_info = await self.context.storage.get_client_info()
 
-        if self.context.current_tokens and self.context.current_tokens.expires_in:
+        if self.context.current_tokens and self.context.current_tokens.expires_in is not None:
             self.context.update_token_expiry(self.context.current_tokens)
 
         self._initialized = True