graphics/lensfun: Add patch to fix segfaults in lensfun

Apply unreleased lensfun commit 6142618 as a patch to
fix segfaults in lensfun when processing Nikon D750 NEF
raw files with ufraw.

PR: 278565
Reported by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Tested by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Approved by: danfe (maintainer)