security: Bug fixing

Change-Id: I809fb456c7759f925f28259d3967f49490dc2262
diff --git a/tools/ndnsec.cpp b/tools/ndnsec.cpp
index eb0877a..ba83dac 100644
--- a/tools/ndnsec.cpp
+++ b/tools/ndnsec.cpp
@@ -46,6 +46,12 @@
 
 int main(int argc, char** argv)
 {
+  if(argc < 1)
+    {
+      std::cerr << ndnsec_helper << std::endl;
+      return 1;
+    }
+
   std::string command(argv[1]);
   
   if(command == "help") { std::cerr << ndnsec_helper << std::endl; }