Fix member call on null pointer, found by sanitizer buildbot.
Fix member call on null pointer, found by sanitizer buildbot.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@279571 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit ed0c7d6ff0e1859c6e883844579ba2794a848e50)

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang