HTML editor crashes for 'str' object has no attribute 'name'

When opening the HTML editor, this traceback is raised:

Traceback (most recent call last):
  File "/home/ced/Projects/tryton/trytond/trytond/protocols/wrappers.py", line 208, in wrapper
    result = func(request, pool, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ced/Projects/tryton/trytond/trytond/protocols/wrappers.py", line 264, in wrapper
    result = func(request, pool, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ced/Projects/tryton/trytond/trytond/ir/routes.py", line 80, in html_editor
    'model': field.model.name,
             ^^^^^^^^^^^^^^^^
AttributeError: 'str' object has no attribute 'name'

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