Excel's find macro is able to search for an empty string
and find an empty cell, without giving a script error.

LibreOffice was raising a "missing params" error if it was passed
an empty string to search for, causing execution failure,
a misleading error code, and failing to find an empty cell.

Also fixed the other copy/paste error codes to indicate
that this is the find function, not the replace function.

Also added a sanity control line to the VBA test.  First select
cell A1 - instead of assuming that no one has touched the
file.

Change-Id: Iabbac7333c37886a667ab5670af819b1cd53c086
Reviewed-on: https://gerrit.libreoffice.org/44618Reviewed-by: Justin Luth <justin_luth@sil.org>
Tested-by: Justin Luth <justin_luth@sil.org>
Tested-by: Jenkins <ci@libreoffice.org>