Fixed segmentation fault when a CFGBlock has NULL successor.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@174182 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/AnalysisBasedWarnings.cpp b/lib/Sema/AnalysisBasedWarnings.cpp
index b362239..5443edb 100644
--- a/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/lib/Sema/AnalysisBasedWarnings.cpp
@@ -714,7 +714,7 @@
         for (CFGBlock::const_succ_iterator I = P->succ_begin(),
                                            E = P->succ_end();
              I != E; ++I) {
-          if (ReachableBlocks.insert(*I))
+          if (*I && ReachableBlocks.insert(*I))
             BlockQueue.push_back(*I);
         }
       }