ripple/rippled — pull request #691 by nbougalis (2014-11-06 23:28:02+00:00)
Title: Fix missing 'else' when handling sfMessageKey

When clearing out a message key the transactor would incorrectly
create an empty `sfMessageKey` field instead of simply deleting
the field.

[**Transaction Processing Change**]

Reviews: @JoelKatz, @ximinez