```ruby
class Api::V0::UsersController < Api::V0::ApiController

  def me
    respond_with current_user
  end

  def search
    @users = User.where("first_name LIKE ? or username LIKE ? or last_name LIKE ?", "%#{ params[:q].capitalize }%", "%#{ params[:q] }%", "%#{ params[:q].capitalize }%")
    render json: @users, each_serializer: UserSerializer
  end

end
```

Add safe operator & for capitalizing params
user
```ruby
class Api::V0::UsersController < Api::V0::ApiController

  def me
    respond_with current_user
  end

  def search
    @users = User.where("first_name LIKE ? or username LIKE ? or last_name LIKE ?", "%#{ params[:q]&.capitalize }%", "%#{ params[:q] }%", "%#{ params[:q]&.capitalize }%")
    render json: @users, each_serializer: UserSerializer
  end

end
```
assistant