[analyzer] Use lazily created buffer in EmptyLocalizationContextChecker

Fix a crash when relexing the underlying memory buffer to find incorrect
arguments to NSLocalizedString(). With precompiled headers, the raw
buffer may be NULL. Instead, use the source manager to get the buffer,
which will lazily create the buffer for precompiled headers.

rdar://problem/27429091

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@280174 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit cf632c9ffd8c80344aac9876748db66ddd9b516d)
3 files changed