Debugger entered--Lisp error: (wrong-type-argument yas--snippet nil)
  yas--find-next-field(1 nil #s(yas--field :number 1 :start 10 :end 17 :parent-field nil :mirrors nil :transform nil :modified-p nil :next #s(yas--exit :marker 19 :next nil)))
  yas-next-field()
  yas-next-field-or-maybe-expand()
  funcall-interactively(yas-next-field-or-maybe-expand)
  command-execute(yas-next-field-or-maybe-expand)