If Alice and Bob are in state X, where Alice sent Bob some money, Alice can do a unilateral exit by initiating a channel closure in state X-1, i.e. the state before she made that payment. This triggers the 2016 block countdown, during which Bob must broadcast the latest state, unless he is okay with losing his most recent payment from Alice. So neither party is ever "stuck" -- they can exit whenever they want.

If you're specifically asking about the very first state, where there is no prior state for Alice to broadcast, she simply doesn't put her money in the multisig until Bob cosigns her exit transactions. I didn't show this is the video but it's part of my work-in-progress wallet implementation (the code is not released yet).