Breaks when data is an array of integers as strings.
Breaks when data is an array of integers as strings.

'+=' can only append strings so specifying each variable as ints with
'+' fixes this.

nexces/Chart.StackedBar.js,Regaddi/Chart.StackedBar.js,Sistemium/Chart.StackedBar.js,alyahmedaly/Chart.StackedBar.js,wanibani/Chart.StackedBar.js