Add InstructionPointerMemoryNullPointer to breakpad_unittests_disabled

BUG=303960
NOTRY=true
TBR=digit@chromium.org

Review URL: https://codereview.chromium.org/111593002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239760 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239760