Talk about lack of commitment. Sonny Crockett's fiancee got the flu, so Crockett got a new fiancee. Singer Sheena Easton will replace flu-ridden actress Lorraine Bracco in a four-episode "Miami Vice" stint, it was announced Wednesday. Bracco finally relinquished her role opposite Don Johnson after her illness forced a delay in production. Although efforts were made to work around her on the NBC series, "Vice" spokesman Robert Crutchfield explained that Bracco had a film commitment starting Dec. 1, and decided she couldn't do both. Producers--anxious to ready the episodes in time for the November ratings sweeps--lost no time summoning Easton to Miami. The two-time Grammy winner had been a runner-up for the role, Crutchfield explained, "so we weren't back to square one." Hopefully, Easton will get a flu shot before filming starts anew.