prevent empty rwho lines

ruptime

@@ -124,8 +124,13 @@ done)
 	    u=$(printf "%-28s %s %s\n" "$k" "$ac" "$nu" | openssl enc -A -a -aes-192-cbc -pbkdf2 -pass env:KEY -in - -out -)
 	;;
 	rwho)
-	    w=$(who |sed "s/ [a-zA-Z:]/ $(eval "$HOSTNAMECMD"):&/1;s,: ,:,1")
-	    u=$(printf "%s\n" "$w" | openssl enc -A -a -aes-192-cbc -pbkdf2 -pass env:KEY -in - -out -)
+            w=$(who |sed "s/ [a-zA-Z:]/ $(eval "$HOSTNAMECMD"):&/1;s,: ,:,1")
+            wl=$(echo -n "$w"|wc -l)
+            if [ ${wl} != 0 ]; then
+                u=$(printf "%s\n" "$w" | openssl enc -A -a -aes-192-cbc -pbkdf2 -pass env:KEY -in - -out -)
+            else
+                exit 0
+            fi
 	;;
 	rbench)
 	    dt=date