Dec 2 (Reuters) - Ryan Christie's goal in first-half stoppage time was enough for Celtic to secure their seventh straight domestic trophy as they beat Aberdeen 1-0 to win the Scottish League Cup at Hampden Park on Sunday.After Gary Mackay-Steven was carried off with a head injury, Christie pounced in the fifth minute of additional time in the first half to fire home the winner.Celtic could have made the margin of victory more comfortable but Scott Sinclair's second-half penalty was saved by Aberdeen goalkeeper Joe Lewis.Aberdeen never really looked like getting back into the match, with Celtic picking up an 18th Scottish League Cup crown on the same day as rivals Rangers won 2-1 at Hearts to go top of the Scottish Premiership. (Reporting by Peter Hall; editing by Clare Fallon)