Callum Robinson's first-half goal ended Preston's run of three successive defeats and inflicted on leaders Bristol City a first home loss since February.It was a second successive setback for Steve Cotterill's side, who squandered some key chances to crash to a second straight league defeat.The visitors took the lead when Chris Humphrey's pinpoint low cross from the right left the unmarked Robinson with a simple tap-in from six yards.City should have been in front by then. Aaron Wilbraham ran on to Luke Freeman's eighth-minute pass and rounded goalkeeper Thorsten Stuckmann only to shoot wide with the goal at his mercy.Aden Flint side-footed narrowly wide for the hosts, but Preston grew into the game and Robinson shot straight at home keeper Frank Fielding after 39 minutes when he might have doubled the visitors' lead.The second half saw Kieran Agard miss a good chance for City and Flint go close again with a header, while Preston substitute Kevin Davies should have made it 2-0 to the Lancashire side when shooting tamely at Fielding after 66 minutes.