Fixed callback execution error on SwitchControlGenerator

Fixes a bug in log:

[2014-09-09 22:13:29.827] Callback execution error: TypeError: Cannot read property 'join' of undefined
    at SwitchControlGenerator.handler (automation/modules/SwitchControlGenerator/index.js:151:22)
    at ZDataHolder.<anonymous> (automation/modules/SwitchControlGenerator/index.js:65:26)