The burrito chain just lost its CEO, but some see a buying opportunity.It's been a wild week for Chipotle (CMG 2.69%) after star CEO Brian Niccol stepped down to take the top job at Starbucks.Shares of the burrito roller plunged on the news, falling as much as 14% before closing the session down 7.5%. Niccol does leave a void at the burrito chain, but Wall Street doesn't seem too alarmed.In fact, some analysts see the sell-off as a buying opportunity. Wedbush turns bullish on ChipotleWedbush just upgraded i ...