Added support for optional listener callbacks. Fixed bug where interpreter would break when listener was added and model includes targetless transition.
Added support for optional listener callbacks. Fixed bug where interpreter would break when listener was added and model includes targetless transition.

mattoshry/SCION-CORE,mattoshry/SCION-CORE,mattoshry/SCION-CORE,jbeard4/SCION-CORE,mattoshry/SCION,mattoshry/SCION-CORE,jbeard4/SCION,mattoshry/SCION,mattoshry/SCION-CORE,jbeard4/SCION,jbeard4/SCION,mattoshry/SCION