Rename some mail merge variables

Fixes the variable name typo pSourrceDocSh and renames bLoop to
bNoError to represent the variables function.

Change-Id: Iba688ed0fb40c0c3947da1b21beb00c67a10ff09
Reviewed-on: https://gerrit.libreoffice.org/7431
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>