[Quick Sign] Fix previous button when navigating between pages

[bnchi]

When a user is at the end of the pdf pages the previous button is set to disabled and the button doesn't work anymore this should be a small fix.

[mkhatib]

@bnchi let me know if you can't merge the PR after I approve it

[bnchi]

@mkhatib I'm not able to merge, here's my email in case you need to add bnchifahmi@gmail.com

[mkhatib]

Just added you to the repo collaborators, can you merge now?