AlliedModders - strip weapons

Well i had my own script to just drop the weapons
But you can't drop knife or he grenade
So i need to know how to remove them because my code looks like below using strip_user_weapons
when player is a chicken it strips weapon, so all weapons are stripped but then when I'm not chicken anymore i can't pick up primary weapon.. :S

Code:

public weapon_switch(id) {
    if(is_chicken[id] == true) {
        strip_user_weapons(id);
    }
    
    return PLUGIN_CONTINUE
}