In Text-rewriting add an option to not add modification when entry is empty

[Former user]

Original [issue 100](https://code.google.com/p/okapi/issues/detail?id=100) created by @ysavourel on 2009-07-26T22:57:44.000Z:

In the Text rewriting utility, add an option that allows to not make modifications to the entries that are empty in the source.

[Former user]

Comment [1.](https://code.google.com/p/okapi/issues/detail?id=100#c1) originally posted by @ysavourel on 2010-05-26T14:33:13.000Z:

Done. Will be in M7