Whittier historic preservation activists have won their court battle to spare the Depression-era Whittier Theater from demolition until an environmental impact report can be prepared. Los Angeles Superior Court Judge Warren Deering on Wednesday issued a preliminary injunction barring the city or property owner Peter Doerken from destroying the theater until the report can be completed, a process expected to take several months. City officials said the theater suffered irreparable damage in the October earthquakes and should be destroyed because it is a public hazard. Doerken wants to level the theater to build a multimillion-dollar shopping plaza. Michael Sullens, president of the Whittier Conservancy, said the injunction will give his group time to develop a plan for buying the theater and restoring it as a regional performing arts center.