Does Florida v. Harris stand for the proposition that narcotics sniffing canines may be trained to alert to residual odor, i.e. the absence of narcotics, and still comply with the Constitutional protections of the Fourth Amendment?

QUESTIONS PRESENTED 1. Does Florida v. Harris stand for the proposition that narcotics sniffing canines may be trained to alert to residual odor, i.e. the absence of narcotics, and still comply with the Constitutional protections of the Fourth Amendment? 2. Does an attempted offense meet the requirements of the elements clause of the Armed Career Criminal Act's definition of violent felony under 18 US.C. § 924(e)(2)(B)(i)?