The QueryCellStyleInfo event of the GridGroupingControl can be handled to hide the ChildTable that does not have any record to show up. The idea is to change the CellType of the RecordPlusMinusCell to static, so that the plus/minus button disappears and you cannot expand the empty ChildTable.
After applying the properties, the grid looks like the following screenshot.
Figure 1: Child tables hidden when there is no record
This page will automatically be redirected to the sign-in page in 10 seconds.