Viserion was killed. Wights react to aggression. They're only defending the Night King's domain. The stone showed the passage on ice was safe. Daenerys was wearing Ghost's pelt in this episode (yes, I know you didn't ask).

ya they thought the ice would crack but slowly started to take the chance once the rock didn't break it. plus they are simple minded dead things.

didn't realize dany was wearing ghosts pelt.. how'd you know that and i wonder if that's like her wearing Jons varsity jacket cuz she likes him?? ha