lrc server crash ( in an experimental try with Ipad)

[saeednm]

version info :
ubuntu 16.04
nodejs: 4.2.6~dfsg-1ubuntu4
xbacklight 1.2.1-1build1
xdotool 1:3.20150503.1-2

lrc-server starts successfully. But after I connect to it with the client on Ipad, it crashes.
Here is the log :

/opt/lrc-server/lrc.js:104
backlight = backlight[1].replace(/^\s+|\s+$/g, "");
^
TypeError: Cannot read property 'replace' of undefined
at /opt/lrc-server/lrc.js:104:41
at ChildProcess.exithandler (child_process.js:204:7)
at emitTwo (events.js:87:13)
at ChildProcess.emit (events.js:172:7)
at maybeClose (internal/child_process.js:821:16)
at Process.ChildProcess._handle.onexit (internal/child_process.js:211:5)

Another time with a little different log :

/opt/lrc-server/lrc.js:104
backlight = backlight[1].replace(/^\s+|\s+$/g, "");
^
TypeError: Cannot read property 'replace' of undefined
at /opt/lrc-server/lrc.js:104:41
at ChildProcess.exithandler (child_process.js:204:7)
at emitTwo (events.js:87:13)
at ChildProcess.emit (events.js:172:7)
at maybeClose (internal/child_process.js:821:16)
at Socket. (internal/child_process.js:319:11)
at emitOne (events.js:77:13)
at Socket.emit (events.js:169:7)
at Pipe._onclose (net.js:469:12)