I agree with Rusty that this is an error. However, many native speakers make it, and it's become a part of daily language. Many people don't even realize it's an error, and avoid "les" believing "le" sounds more educated. Go figure.
- Le dije a los niños que vengan a comer. (It should be "les dije".)
- No le echaste agua a las plantas. (Correct: "no les echaste".)
- ¿Por qué se enojan conmigo, si no le hice nada a los perros? ("No les hice nada".)