Add test showing merge paragraph assert with some exotic odf elements
Allow merge paragraph to handle unexpected nodes near paragraph boundaries

getTextElements may return some unexpected text nodes if the step filters
haven't correctly identified the first/last step in the paragraph. Rather
than failing completely in this case, simply log the unexpected items and
skip them.

getTextElements itself still needs to be fixed in these cases, but the
harm caused by such mistakes is slightly reduced in this instance.
Merge pull request #771 from peitschie/merge-p-fields

Allow merge paragraph to handle unexpected nodes near paragraph boundaries
Add test demonstrating foreign elements are discarded on paragraph merge
Fix preservation of foreign elements on paragraph merge

This behaviour was working prior to the merge paragraph operation being
introduced. A new edge case was introduced related to cleaning up empty
spans that caused this to regress.