Fix compilation errors

cli/threadexecutor.cpp

@@ -369,7 +369,7 @@ void ThreadExecutor::reportInternalChildErr(const std::string &childname, const
                               Severity::error,
                               "Internal error: " + msg,
                               "cppcheckError",
-                              false);
+                              Certainty::normal);
 
     if (!mSettings.nomsg.isSuppressed(errmsg.toSuppressionsErrorMessage()))
         mErrorLogger.reportErr(errmsg);

lib/errortypes.h

@@ -43,7 +43,7 @@ struct InternalError {
 class CPPCHECKLIB Certainty {
 public:
     enum CertaintyLevel {
-        normal, inconclusive, experimental
+        normal, inconclusive, safe, experimental
     };
 };