The state’s public-safety unions have scored a potential win in their end-of-session push for a law that will make it easier for police officers and firefighters to get disability pensions that pay them two-thirds pay, tax-free for life. The Rhode Island House of Representatives on a 53-to-8 vote approved legislation to equate an “illness sustained while in the performance of duty” with an on-the-job injury so more firefighters can qualify for benefits they have, in some past cases, been denied. State Treasurer Seth Magaziner’s office told lawmakers the legislation would have an “immaterial impact? on the state-run pension system because public-safety workers with illnesses directly attributable to their jobs already qualify.