California firefighters battled a massive fire that erupted Thursday at a former restaurant on the city’s historic pier. A vacant restaurant at the end of a Southern California pier was engulfed in flames Thursday afternoon, sending a column of smoke billowing over the pier. The fire at Oceanside Pier in Oceanside, in northern San Diego County, broke out at around 3 p.m. at or near a building that once housed Ruby’s Diner. A fish shack at the end of the pier, Brine Box, said its staff was safely evacuated. “What’s happening on the pier is sad and scary. We want you to know that our team is saf…