While romancing “Avatar” star Zoe Saldana, Sexiest Man Alive Bradley Cooper rolled solo to a premiere of Liam Neeson’s survival thriller “The Grey” Wednesday night. Sources tell us the “Hangover” star, spotted leaving an LA house with Saldana early one morning this week, was due to attend his 37th birthday bash last night at Wolfgang Puck’s new restaurant at the Hotel Bel-Air. Saldana will start filming “Star Trek” this week. Also walking the red carpet for “The Grey” were Kristen Bell, Dermot Mulroney, Minnie Driver and Neeson’s “Taken” sequel co-stars Maggie Grace and Famke Janssen. Neeson presented a People’s Choice Award to Emma Stone in downtown Los Angeles before he ducked out and headed to LA Live for his own movie premiere. At an after-party at The Palm, the steakhouse unveiled caricatures on the wall of Neeson and director Joe Carnahan. Cooper, sporting shaggy stubble and a motorcycle jacket, headed off alone to hit a pre-Golden Globes party.