I'm Getting Warnings For Negative Attitude For No Reason

Hey guys, I play League of Legends from Season 1 and I never got reported or banned before. Today (7/9/2015) after the ending my games I'm getting warnings for getting reported for negative attitude. The weird thing is that I didn't chat, troll, flamed on the games .... Can it be a riot's bug ? Thanks =) _R.I.P Riot_
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