fixes averageblur bad idx shift and divide
fixes averageblur bad idx shift and divide

cedricpinson/osgjs,hishamabdelrahman/osgjs,kkuunnddaannkk/osgjs,jtorresfabra/osgjs,jmirabel/osgjs,gideonmay/osgjs,kkuunnddaannkk/osgjs,gideonmay/osgjs,cedricpinson/osgjs,jtorresfabra/osgjs,jmirabel/osgjs,jtorresfabra/osgjs,gideonmay/osgjs,hishamabdelrahman/osgjs,cedricpinson/osgjs,jmirabel/osgjs,hishamabdelrahman/osgjs,kkuunnddaannkk/osgjs