Pivot - Filters for null values

If any of the filters has null values in the data, processFilters method getting failed.

in pivot_unminified.js (v 4.3.0, line # 342)
I need to change this line from

for (var s in r) o = r[s][e], webix.isUndefined(o) || a[o] || (n.push({

to

for (var s in r) o = r[s][e] !== null? r[s][e] :"", webix.isUndefined(o) || a[o] || (n.push({

to make it work.

Is there any way I can override this method?