Make the CIndex API more resilient to being used on invalid code.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@98981 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/CIndex/CXCursor.cpp b/tools/CIndex/CXCursor.cpp
index 407f44c..cbf9d7e 100644
--- a/tools/CIndex/CXCursor.cpp
+++ b/tools/CIndex/CXCursor.cpp
@@ -266,7 +266,10 @@
 CXCursor cxcursor::MakeCursorObjCClassRef(ObjCInterfaceDecl *Class, 
                                           SourceLocation Loc, 
                                           ASTUnit *TU) {
-  assert(Class && TU && "Invalid arguments!");
+  // 'Class' can be null for invalid code.
+  if (!Class)
+    return MakeCXCursorInvalid(CXCursor_InvalidCode);
+  assert(TU && "Invalid arguments!");
   void *RawLoc = reinterpret_cast<void *>(Loc.getRawEncoding());
   CXCursor C = { CXCursor_ObjCClassRef, { Class, RawLoc, TU } };
   return C;