What mean thing did Sid do at the widow's party in "The Adventures of Tom Sawyer"?

In chapter 34, Tom and Huck are getting ready for the party when Sid comes into the room. He tells them that everybody's been waiting for them, and then he says that Mr. Jones has a surprise for everyone: He plans to announce that it was Huck who tracked the robbers to the widow's house. Tom and Huck are furious, and they accuse Sid of telling Mr. Jones what happened:

"Sid, there's only one person in this town mean enough to do that, and that's you. If you had been in Huck's place you'd 'a' sneaked down the hill and never told anybody on the robbers. You can't do any but mean things, and you can't bear to see anybody praised for doing good ones. There--no thanks, as the widow says"--and Tom cuffed Sid's ears and helped him to the door with several kicks. "Now go and tell auntie if you dare--and to-morrow you'll catch it!"

Tom spoils Mr. Jones's surprise by revealing an even bigger secret: He and Huck are rich!