From ecf2f1593a50e95453d883cbf69d54df409bac4a Mon Sep 17 00:00:00 2001
From: Sergey Sharybin <sergey.vfx@gmail.com>
Date: Mon, 29 May 2017 09:40:43 +0200
Subject: [PATCH] Fix T51646: Motion Tracker instantly crashes

Was a mistake in previous changes.

Weirdly enough, frame reading assumes cache_key is always non-NULL..
---
 intern/libmv/intern/frame_accessor.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/intern/libmv/intern/frame_accessor.cc b/intern/libmv/intern/frame_accessor.cc
index e7fc0ab4883..a741eb88fc7 100644
--- a/intern/libmv/intern/frame_accessor.cc
+++ b/intern/libmv/intern/frame_accessor.cc
@@ -134,6 +134,11 @@ struct LibmvFrameAccessor : public FrameAccessor {
         &width,
         &height);
 
+    if (cache_key == NULL) {
+      // No mask for the given track.
+      return NULL;
+    }
+
     // TODO(sergey): Dumb code for until we can set data directly.
     FloatImage temp_image(float_buffer,
                           height,