ag-grid: Cell class & refreshing data causes an internal error

[x] bug report => see 'Providing a Reproducible Scenario'
[] feature request => do not use Github for feature requests, see 'Customers of AG Grid'
[] support request => see 'Requesting Community Support'

When using cell class (I think) or maybe cell style, upon refreshing the data an exception is seen:

ERROR TypeError: Cannot read properties of undefined (reading 'length')
    at CellCustomStyleFeature.applyClassesFromColDef (ag-grid-community.cjs.js:20788)
    at CellCtrl.refreshCell (ag-grid-community.cjs.js:22001)
    at ag-grid-community.cjs.js:22920
    at Array.forEach (<anonymous>)
    at RowCtrl.onRowNodeDataChanged (ag-grid-community.cjs.js:22919)
    at ag-grid-community.cjs.js:1350
    at Set.forEach (<anonymous>)
    at processEventListeners (ag-grid-community.cjs.js:1345)
    at EventService.dispatchToListeners (ag-grid-community.cjs.js:1355)
    at EventService.dispatchEvent (ag-grid-community.cjs.js:1334)

This appears at this code point which was introduced after version 25.3.0:

    if (this.staticClasses.length) {
        this.staticClasses.forEach(function (className) { return _this.cellComp.addOrRemoveCssClass(className, false); });
    }

This should be (this.staticClasses && this staticClasses.length)

My cell definition ends as follows:

cellClass: this.processEditableClass,

I am happy to send through a plunkr, please provide a link if available. This has to be 26.2.0 however of ag-grid.

Current behaviour. When the data is got the second time (upon paging or filtering) using a datasource the error is seen. If I regress to 25.3.0 the error is no longer present. The version in error is 26.2.0

Expected behaviour.

There should be no error and use the trap above to ensure staticClasses aren’t checked.

Environment Angular, NG12 Windows or Linux

• AG Grid version:*

26.2.0

• Browser: All browsers show this.

• Language:

Typescript 4.4.5