Index: ode/demo/demo_jointPR.cpp
--- ode/demo/demo_jointPR.cpp.orig
+++ ode/demo/demo_jointPR.cpp
@@ -329,7 +329,7 @@ int main (int argc, char **argv)
             {
                 int j = i+1;
                 if ( j >= argc      ||  // Check if we have enough arguments
-                        argv[j][0] == '\0' ||  // We should have a path here
+                        argv[j][0] == 'NULL' ||  // We should have a path here
                         argv[j][0] == '-' ) // We should have a path not a command line
                     Help(argv);
                 else