Anim Montage no animations for some slots at different sections

So I currently have an anim montage for the player casting fireball. It is having a slot for left arm and a slot for right arm (which are fed base locomotion and blended by pelvis l and r respectively with the base locomotion). So if I’m only casting with one hand, the other one is following the locomotion which is an expected and desired behavior. But for my gameplay needs I have two sections in the montage: Attack1 and Attack2 (left and right hand) and I am altering between them (every weapon has a montage used for attacking). Now the problem is, I can’t have no animation in one section and have the animation in other one for the hand that is not used, I need to place the idle anim which is not a desired result. Is there a way to have no animation per section or is there another known workaround?