Default values are ignored by `magic_factory`

Describe the bug

from magicgui import magic_factory
@magic_factory
def factory(arg=None):
    ...
factory()()

This fails with

TypeError: missing a required argument: 'arg' in call to 'factory(arg)'.
To avoid this error, you can bind a value or callback to the parameter:

    factory.arg.bind(value)

Or use the 'bind' option in the magicgui decorator:

    @magicgui(arg={'bind': value})
    def factory(arg): ...

Indeed, this can be circumvented by adding arg={'bind': None} to the magic_factory call, but this is different from the bahviour of @magicgui.

[tlambert03]

ancient history!! 😃

[tlambert03]

different, will take a look.