Whipple shields are cheap and effective. The impact does indeed impart a lot of kinetic energy, but on a thin sacrificial layer. This breaks the projectile into thousands or millions of tinier projectiles in an expanding cone of debris. As each of those smaller projectiles carries much less kinetic energy, and they impact your craft over a much larger area, the damage to the hull is minimized or even eliminated.

Since a solar sail is just a huge sheet of plastic coated in aluminum, any impact with the sail will tend to leave just a pinhole, or possibly a tear. You do need to design your sail with ripstops, but the total area lost to the pinholes will tend to be quite small.