Shockwave would acknowledge Starscream's existence and all, but Megatron just addressed him. So he's just going to make eye contact with the Decepticon warlord and conveniently ignore that twitchy, gray Cybertronian shaped thing in his periphery.

"A problem I will begin to address, my liege, after acquiring more detailed data of the damage to your ship," beginning there would be the most logical choice, after all. There can't be much conquering done with their butts parked in a desert somewhere.