st/mesa: set compressed_data to NULL when freed
Reported-by:Karol Herbst <kherbst@redhat.com> Fixes: b6db703e ("st/mesa: make texture views inherit compressed_data storage") Reviewed-by:
Karol Herbst <kherbst@redhat.com> Tested-by:
Dave Airlie <airlied@redhat.com> Part-of: <mesa/mesa!5821> (cherry picked from commit 51bdaf0b)