Store a local copy of the relevant field for both the null check and the
following access to avoid an asynchronous nullify in between, resulting
in an NPE.

This is exactly the same fix as in bug 526368.

Change-Id: Ic1ca16a258ffc164f010a94e2a6ae4de34a91e1c
Signed-off-by: Michael Keppler <Michael.Keppler@gmx.de>