fix check for command line args: if(argc>=1) -> if(argc>1)

Former-commit-id: 44b95370810ea2603346c4e09d81f4625cf37c39

tutorial/203_CurvatureDirections/main.cpp

@@ -17,7 +17,7 @@ int main(int argc, char *argv[])
 {
   using namespace Eigen;
   std::string filename = "../shared/fertility.off";
-  if(argc>=1)
+  if(argc>1)
   {
     filename = argv[1];
   }