Allow `dape-key-prefix` to be nil.

[milanglacier]

Any comments on this patch?

I am an evil user and global-set-key does not work with evil's normal state so I will use other functions to bind the prefixes, allowing set this key to nil would definitely help evil users.

[svaante]

Hi! The change makes sense to me and thanks for contributing :)

But before that do you have by any chance done the Copyright assignment https://www.fsf.org/licensing/contributor-faq

It's needed for contributions to packages on GNU ELPA, which is I is where I am hoping this package will be at some point.

I think this counts as an trivial patch, but I am not 100%.

[milanglacier]

I can complete the FSF assignment and will let you know once I completed, thanks.

[svaante]

Hello! Is there any progress in getting the FSF assignment? If not maybe we can merge this as an non trivial change.

[timcharper]

Per the rule cited in the other PR,

https://www.gnu.org/software/emacs/manual/html_node/emacs/Copyright-Assignment.html

We can accept small changes (roughly, fewer than 15 lines) without an assignment. This is a cumulative limit (e.g., three separate 5 line patches) over all your contributions.

Might be unnecessary.

[joaotavora]

Recommend you add the line

Copyright-paperwork-exempt: yes

In a separate line of the commit messages, to clearly mark these changes

[svaante]

Makes sense! @milanglacier if you fix the merge conflicts we can merge this

[milanglacier]

Thanks for the update. I have update the commit and resolve the commit, should be able to merge.