You can only apply scalars to the if port of action subsystems. Consider your example where you test:
out1_of_if_block = u1 == [1 2] = [1 0]
What do you expect the If Action Subsystem2 to do when [1 0] is applied to the action port?
Perhaps inside of the 'If' block, you would want to do something more like this:
u1(1) == 1
