Any source code by Whonix shouldn’t be capable of crashing the kernel. If it does so anyhow, that’s kernel bugs.
At time of writing, Whonix doesn’t change / modify any kernel source code. Less so for Qubes.
The only place where any action might be taken based on such a bug report is the Qubes issue tracker and maybe the Xen and or Linux upstream issue tracker.
Related:
What to post in this Qubes-Whonix forum and what not.