[analyzer] Fix a crash in plist-html generation introduced in r162939.
[analyzer] Fix a crash in plist-html generation introduced in r162939.

Basically, do the correct thing to fix the XML generation error, rather
than making it even worse by unilaterally dereferencing a null pointer.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@162964 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang