Client Crash and my account got a 20 minutes LeaverBuster

I hate it when my client crash and I got a 20 mins LeaverBuster....like, why do my account got a 20 mins leaver buster when im not even in a match? the leaver buster fact is it happen when you AFK....please help me I really2 love to Play LOL but I hate to wait for 20 minutes when its not my fault