[libclang] Add defensive checks to make sure we don't try to dereference
a null pointer after getCursorDecl() is called. rdar://10298421.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@146312 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/CIndexUSRs.cpp b/tools/libclang/CIndexUSRs.cpp
index 32c4db6..40d4fb1 100644
--- a/tools/libclang/CIndexUSRs.cpp
+++ b/tools/libclang/CIndexUSRs.cpp
@@ -845,6 +845,9 @@
 
   if (clang_isDeclaration(K)) {
     Decl *D = cxcursor::getCursorDecl(C);
+    if (!D)
+      return createCXString("");
+
     CXTranslationUnit TU = cxcursor::getCursorTU(C);
     if (!TU)
       return createCXString("");