Rocker David Crosby's lawyers have been busy. Late last week, his prior drug and weapon possessions convictions were reversed by a Texas state judge. At almost the same time, Crosby was settling a lawsuit filed against former friends alleging that they owed him $18,000 in back rent for staying in his Mill Valley, Calif., home while he served his prison term in Texas. Peter and Ellen Dodd stated in court documents that they lived in the house since February, 1986, at Crosby's request. They claimed that the $1,500-per-month lease agreement payments were to be offset by work to clean the house that they called "an enormous litter box."