Allows y === null in drawText.
Allows y === null in drawText.

Allow leaving Y as null in the dynamicTexture.drawText function and centers the text vertically instead.
RaananW/Babylon.js,abow/Babylon.js,BabylonJS/Babylon.js,jbousquie/Babylon.js,abow/Babylon.js,Kesshi/Babylon.js,sebavan/Babylon.js,Kesshi/Babylon.js,Temechon/Babylon.js,jbousquie/Babylon.js,NicolasBuecher/Babylon.js,RaananW/Babylon.js,Kesshi/Babylon.js,Hersir88/Babylon.js,sebavan/Babylon.js,Hersir88/Babylon.js,Hersir88/Babylon.js,sebavan/Babylon.js,Temechon/Babylon.js,abow/Babylon.js,NicolasBuecher/Babylon.js,jbousquie/Babylon.js,BabylonJS/Babylon.js,BabylonJS/Babylon.js,RaananW/Babylon.js,NicolasBuecher/Babylon.js,Temechon/Babylon.js