Review `condition` types

[sergeysova]

[sergeysova]

then and else allows Unit<void> in union (Unit<T> | Unit<void> or Unit<T | void> doesnt matter). When Event<T> passed to else it comes as T assigning to T | void, but also it is requires T | void for else, but passed T.

[ainursharaev]

then and else allows Unit<void> in union (Unit<T> | Unit<void> or Unit<T | void> doesnt matter). When Event<T> passed to else it comes as T assigning to T | void, but also it is requires T | void for else, but passed T.

Could you please reproduce the issue?