Guard against null gridApi in onSortChanged

[SAY-5]

Fixes #466.

onSortChanged is the only grid event handler that dereferences gridApi without a null check. When a grid is created with a sort applied at init time (via initialState.sort.sortModel), AG Grid queues the sortChanged event during grid creation and flushes it on a setTimeout tick that can run before React commits the setGridApi update from onGridReady. The closure then sees gridApi === null and gridApi.isDestroyed() throws an uncaught TypeError.

This aligns the guard with every sibling handler (onPaginationChanged, onRowDataUpdated, etc.), which already use if (gridApi && !gridApi?.isDestroyed()).

The same handler is also bound to onRowDragEnd, so the guard covers that path too.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud