Prevent display corruption when edit cell is active in a group.
Prevent display corruption when edit cell is active in a group.

When using a modified version of the interactive grouping and aggregates
example having an active edit cell when trying to collapse a group
caused my display to be corrupted.  This change addresses that issue.

GerHobbelt/SlickGrid,GerHobbelt/SlickGrid,GerHobbelt/SlickGrid