Remove the CFGElement "Invalid" state.

Use Optional<CFG*> where invalid states were needed previously. In the one case
where that's not possible (beginAutomaticObjDtorsInsert) just use a dummy
CFGAutomaticObjDtor.

Thanks for the help from Jordan Rose & discussion/feedback from Ted Kremenek
and Doug Gregor.

Post commit code review feedback on r175796 by Ted Kremenek.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175938 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/AnalyzerStatsChecker.cpp b/lib/StaticAnalyzer/Checkers/AnalyzerStatsChecker.cpp
index 217d467..9af0a5a 100644
--- a/lib/StaticAnalyzer/Checkers/AnalyzerStatsChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/AnalyzerStatsChecker.cpp
@@ -123,14 +123,14 @@
     const BlockEdge &BE =  I->first;
     const CFGBlock *Exit = BE.getDst();
     const CFGElement &CE = Exit->front();
-    if (CFGStmt CS = CE.getAs<CFGStmt>()) {
+    if (Optional<CFGStmt> CS = CE.getAs<CFGStmt>()) {
       SmallString<128> bufI;
       llvm::raw_svector_ostream outputI(bufI);
       outputI << "(" << NameOfRootFunction << ")" <<
                  ": The analyzer generated a sink at this point";
-      B.EmitBasicReport(D, "Sink Point", "Internal Statistics", outputI.str(),
-                        PathDiagnosticLocation::createBegin(CS.getStmt(),
-                                                            SM, LC));
+      B.EmitBasicReport(
+          D, "Sink Point", "Internal Statistics", outputI.str(),
+          PathDiagnosticLocation::createBegin(CS->getStmt(), SM, LC));
     }
   }
 }