elasticsearch/elasticsearch — pull request #7032 by jpountz (2014-07-25 10:22:31+00:00)
Title: Mappings: Enforce non-null settings.

No that we are using the index created version to make index-time decisions,
assuming that the version is the current version when settings are null is
very error-prone. Instead we should ensure that settings are always non-null
and contain the version when the index was created.