enter and leave doesn't work

[cdelmas]

When using enter and leave to make the bot react on these events,

robot.enter (res) ->
    res.send res.random enterReplies
  robot.leave (res) ->
    res.send res.random leaveReplies

I get the following error:

ERROR TypeError: Cannot read property 'toLowerCase' of undefined
  at Brain.userForName (xxxx\basic\node_modules\hubot\src\brain.coffee:120:17, <js>:106:23)
  at Matteruser.send (xxxx\basic\node_modules\hubot-matteruser\src\matteruser.coffee:101:16, <js>:160:31)
  at runAdapterSend (xxxx\basic\node_modules\hubot\src\response.coffee:82:34, <js>:87:50)
  at allDone (xxxx\basic\node_modules\hubot\src\middleware.coffee:44:37, <js>:34:16)
  atxxxx\basic\node_modules\async\lib\async.js:274:13
  at Object.async.eachSeries (xxxx\basic\node_modules\async\lib\async.js:142:20)
  at Object.async.reduce (xxxx\basic\node_modules\async\lib\async.js:268:15)
  at xxxx\basic\node_modules\hubot\src\middleware.coffee:49:7, <js>:37:22
  at _combinedTickCallback (internal/process/next_tick.js:67:7)
  at process._tickCallback (internal/process/next_tick.js:98:9)

It looks like it is the same problem than #32