FTX sought a U.S. bankruptcy court's help amid a battle over ownership of about $450 million worth of stock in Robinhood Markets (HOOD), according to a filing Thursday.At issue are about 56 million shares of the brokerage owned by Emergent Fidelity Technologies Ltd., a corporate entity organized in Antigua and Barbuda and 90% controlled by former FTX CEO Sam Bankman-Fried, according to the filing.Three parties, the filing says, have tried to get control of those shares: BlockFi (a lender that FTX had helped prop up earlier this year), Yonathan Ben Shimon (an FTX creditor appointed as a receive