fix crash on export of fdo68639-2.ods to xls with invalid mnLastIdx

mnLastIdx doesn't get reset when the color list is reset, the code already
acknowledges that mnLastIdx is the last set index but that it may not be a
valid position, so only set rnIndex if mnLastIdx is valid and the data at that
pos is the desired data.

Change-Id: I57ce32fd1a13bfe9049ed94be34229c8c2808b8e
(cherry picked from commit 6c3b1361a97f5219f90bf2f09f3c3f2b70b8e30e)
Reviewed-on: https://gerrit.libreoffice.org/15319
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>
(cherry picked from commit e3c0596857ed8713de829ac9875892312f595504)
Reviewed-on: https://gerrit.libreoffice.org/15443
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Reviewed-by: David Tardon <dtardon@redhat.com>

0 files changed, 0 insertions, 0 deletions