Fix CIndex crash on invalid code reported in <rdar://problem/7833619>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@100589 91177308-0d34-0410-b5e6-96231b3b80d8

test/Index/invalid-code-rdar_7833619.m

@@ -0,0 +1,4 @@
+// RUN: c-index-test -test-load-source all %s
+// All we care about in this test is that it doesn't crash.
+typedef r7833619_a (*r7833619_b)(r7833619_c *r7833619_d, r7833619_c *r7833619_e);
+

tools/CIndex/CIndex.cpp

@@ -814,8 +814,9 @@ bool CursorVisitor::VisitFunctionTypeLoc(FunctionTypeLoc TL) {
     return true;
 
   for (unsigned I = 0, N = TL.getNumArgs(); I != N; ++I)
-    if (Visit(MakeCXCursor(TL.getArg(I), TU)))
-      return true;
+    if (Decl *D = TL.getArg(I))
+      if (Visit(MakeCXCursor(D, TU)))
+        return true;
 
   return false;
 }