In vetoing a bill last year that would have curtailed some deportations under the federal program known as Se Communities, Gov. Jerry Brown explained that he feared it would block immigration authorities from removing some genuinely dangerous criminals. Now, a new bill is moving through the Legislature, and it attempts to fix the problems of its predecessor. That bill, known as the Trust Act, would still allow police to hold immigrants convicted of serious crimes, including some misdemeanors, for up to 48 hours while they await transfer to federal custody. But it would prohibit police from detaining those arrested for minor offenses — such as disturbing the peace, street vending or traffic violations — solely for immigration purposes.