[kubuntu] shutdown freezes whole laptop

just installed couple days ago beta 2 version of kubuntu. (I tried ubuntu gnome but it didnt work at all, that whole another thing )

now everytime I shutdown my computer it freezes to keel panic lookalike screen and computer stays on.
couple lines from hang:
"BUG: unable to handle keel NULL pointer dereference
IP: [ffff.....fae2] amdgpu_vm_grab_id+0x122/0x310 [amdgpu]

my laptop is Toshiba*Satellite S50B14M

model name : Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz
00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 0b)
09:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Topaz XT [Radeon R7 M260/M265] (rev ff)

I dont even know which GPU Kubuntu uses..