By Gabriela Baczynska, Krisztina Than and Andrew Gray BRUSSELS (Reuters) -European Union leaders unexpectedly agreed on Thursday to open membership talks with Ukraine, something Hungarian Prime Minister Viktor Orban for weeks had vowed to block. EU diplomats and officials said Orban agreed to leave the room, knowing the other leaders would go ahead and vote on Ukraine. Orban confirmed on Facebook that he had abstained from the vote on what he called a “bad decision”. Ukrainian President Volodymyr Zelenskiy welcomed the decision. “This is a victory for Ukraine. A victory for all of Europe. A vi…