Expanding/collapsing groups when cell merging is enabled throws error

[skrustev]

Description

When cell merging is enabled, expand/collapse of groups throws error.

• igniteui-angular version: 20.x
• browser: any

Steps to reproduce

1. Open the gridCellMerging demo
2. Group by Order Date
3. Try to collapse any group row

Result

The following error is thrown and further expand/collapse is not possible:

ERROR TypeError: Cannot read properties of undefined (reading 'get')
    at grid.pipes.ts:119:58
    at Array.forEach (<anonymous>)
    at grid.pipes.ts:118:29
    at Array.forEach (<anonymous>)
    at _IgxGridUnmergeActivePipe.transform (grid.pipes.ts:115:26)
    at pureFunctionVInternal (debug_node.mjs:28852:53)
    at Module.ɵɵpipeBindV (debug_node.mjs:29072:11)
    at IgxGridComponent_Template (grid.component.html:89:45)
    at executeTemplate (debug_node.mjs:9040:9)
    at refreshView (debug_node.mjs:10076:13)

Expected result

There should be no error when expanding/collapsing groups

Attachments

Attach a sample if available, and screenshots, if applicable.