fdo#71749: sw: WW8: don't loop on tables in footnotes

(regression from ee1db992b98378b5e2f5e9aa8af0e36c375e582f)

Change-Id: Id10b6fb8e9e3697b10a1df605cb48d94a55ad207
fdo#71450 fdo#71698: ODF import: fix frame name corner cases

Trying to set a name that is already in use will throw an exception (and
set a different, generated name); if there is actually no name in the
file then there's no point trying to set anything.

(regression from b69d152cfa1da868ba960345d72ba78f9f8e1b35)

Change-Id: Ie54d4a830cc23e2853a6efeb81f77dcc788192ea