Blender Git Loki

Crash when deleting NlaTrack

Steps to reproduce:
1) Create an object, animated with shape keys
2) Copy it with Alt-D
3) Push action down to nla track
4) Select that track and delete it

In attached file 1-3 steps are completed.
{F138559}

Alexander (Blend4Web Team)

Reviewers: aligorith

Subscribers: yurikovelenov, Evgeny_Rodygin, valentin_b4w, AlexKowel

Differential Revision: https://developer.blender.org/D1015