Fix the introduced bug in ndn command-line tool

Change-Id: I4eb515d64b287cc86a3a58ed2c34c974017e102e
diff --git a/res/ndn b/res/ndn
index 99bdc07..50f4921 100755
--- a/res/ndn
+++ b/res/ndn
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-if [[ $# -eq 0 ]] || [[ ! -f /Applications/NDN.app/Contents/Platform/"$@" ]] ; then
+if [[ $# -eq 0 ]] || [[ ! -f /Applications/NDN.app/Contents/Platform/"$1" ]] ; then
     echo ERROR: No command or invalid command is specified
     echo
     echo Available commands: