C:\Users\Tom\Desktop\Bot\index.js:355
  member.addRole(role.id).then(member =>{
                      ^

TypeError: Cannot read property 'id' of null
    at Client.<anonymous> (C:\Users\Tom\Desktop\Bot\index.js:355:23)
client.on('messageReactionAdd', (reaction, user) =>{
  if(user.bot)
    return;
  var roleName = reaction.emoji.name;
  var role = reaction.message.guild.roles.find(role => role.name.toLocaleLowerCase() === roleName.toLocaleLowerCase());
  var member = reaction.message.guild.members.find(member => member.id === user.id);
  member.addRole(role.id).then(member =>{
    console.log("Added " + member.user.username + " to a role.");
  }).catch(err => console.error);
});