[pkg-apparmor] Bug#901559: apparmor fails to start with empty features-file=

[Vincas Dargis]

On 6/14/18 10:15 PM, intrigeri wrote:
> Can you try to reproduce on Stretch and sid? If behaviour has changed,
> it's a different matter :)

It fails the same on Stretch, it's not a regression, so it's my mistake. 
Sorry for the noise.

P.S. What's the right way to close BTS bug as invalid?