[libclang] Make sure we don't try to handle a CXCursor_NoDeclFound
passed to clang_findReferencesInFile.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@146211 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/CXCursor.cpp b/tools/libclang/CXCursor.cpp
index b4b9ed9..5117a4d 100644
--- a/tools/libclang/CXCursor.cpp
+++ b/tools/libclang/CXCursor.cpp
@@ -746,8 +746,10 @@
 }
 
 ASTUnit *cxcursor::getCursorASTUnit(CXCursor Cursor) {
-  return static_cast<ASTUnit *>(static_cast<CXTranslationUnit>(Cursor.data[2])
-                                  ->TUData);
+  CXTranslationUnit TU = static_cast<CXTranslationUnit>(Cursor.data[2]);
+  if (!TU)
+    return 0;
+  return static_cast<ASTUnit *>(TU->TUData);
 }
 
 CXTranslationUnit cxcursor::getCursorTU(CXCursor Cursor) {