Added a small fix to allow Stage to have a null canvas reference when inited, so it can be extended more easily.
Added a small fix to allow Stage to have a null canvas reference when inited, so it can be extended more easily.

Signed-off-by: Grant Skinner <59bd0a3ff43b32849b319e645d4798d8a5d1e889@gskinner.com>

mientjan/weasel,EricHodgins/EaselJS,exsodus3249/EaselJS,johnv315/EaselJS,xushuwei202/EaselJS,mientjan/EaselTS,createjs-components/easeljs,andrew168/EaselJS,Teino1978-Corp/https-github.com-Teino1978-Corp-EaselJS,Teino1978-Corp/https-github.com-Teino1978-Corp-EaselJS,bambalaus/EaselJS,8823-scholar/EaselJS,julianromera/EaselJS,markknol/EaselTS,nbellowe/EaselJS,kidaa/EaselJS,johnv315/EaselJS,felipegtx/EaselJS,zhengjiangbin/EaselJS,CreateJS/EaselJS,rhildred/abacus,speedlightconsulting/EaselJS,zhengjiangbin/EaselJS,bambalaus/EaselJS,ytiurin/EaselJS,legendvijay/EaselJS,SpringRoll/EaselJS,ovcharik/EaselJS,abouthiroppy/EaselJS,thinkerchan/EaselJS,nbellowe/EaselJS,briesurrood/EaselJS,ovcharik/EaselJS,andrew168/EaselJS,gitzxon/EaselJS,markknol/EaselTS,mientjan/EaselTS,thinkerchan/EaselJS,felipegtx/EaselJS,ebabel-eu/EaselJS,briesurrood/EaselJS,markknol/EaselTS,rhildred/abacus,speedlightconsulting/EaselJS,julianromera/EaselJS,mientjan/weasel,SpringRoll/EaselJS,kidaa/EaselJS,8823-scholar/EaselJS,xushuwei202/EaselJS,EricHodgins/EaselJS,exsodus3249/EaselJS,abouthiroppy/EaselJS,legendvijay/EaselJS,CreateJS/EaselJS,ebabel-eu/EaselJS,gitzxon/EaselJS,ytiurin/EaselJS