Move order persists after ordering single unit to attack a stack

[dzfischer]

Expected behavior: After unit A attacks stack S and consumes all move points, A should not have any queued orders.

Actual: A has no move points but a queued order to attack S, requiring the player to manually cancel the order as the attack is probably undesirable.

If a single unit attacks an enemy stack on a neighboring tile and successfully kills one enemy unit but cannot enter the tile due to other enemy military units remaining their from the stack, there will be a queued order for the now-exhausted unit to keep trying to move onto the same tile occupied by enemy units next turn. This is often suicidal, and having to make sure to cancel such orders can be irritating. It would be nicer and more intuitive if a unit that attacked a neighboring tile but could not move onto it for whatever reason simply remained on its original tile without any orders for the future. Note that this issue only occurs with a single unit attacking, not when a whole stack is selected.