Dont crash on wrong command line options

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@354 fdac6126-5c0c-442c-9429-916003d36597

src/OpenMesh/Apps/Dualizer/dualizer.cc

@@ -53,6 +53,11 @@ int main(int argc, char **argv)
 {
     MyMesh mesh;
 
+    if ( argc != 2 ) {
+        std::cerr << "Please specify input filename only!" << std::endl;
+        return 1;
+    }
+
     // read mesh from argv[1]
     if ( !OpenMesh::IO::read_mesh(mesh, argv[1]) )
     {