Article page url in chinese language Drupal 7
This error might appear when the MySQL database is encoded as UTF8. In that case, Unicode characters represented with 4 bytes are not accepted. The accepted reply to the following StackOverflow question explains that the database needs to be encoded using the utf8mb4 encoding and the utf8mb4_unicode_ci collation:

https://stackoverflow.com/questions/10957238/incorrect-string-value-when-trying-to-insert-utf-8-into-mysql-via-jdbc

A more complete explanation about the utf8mb4 encoding on MySQL can be found here:

https://mathiasbynens.be/notes/mysql-utf8mb4

In case you need to re-encode your existing Drupal database, there is an experimental Drush command for it at UTF8MB4 Convert.