RequestFactory.toElasticsearchIndicesOptions fails on empty options or wildcard states

[pnowak85]

If you try to create custom IndicesOptions with either an empty set of Option or WildcardState you get an IllegalArgumentException:

java.lang.IllegalArgumentException: Collection is empty

	at java.util.EnumSet.copyOf(EnumSet.java:174)
	at org.springframework.data.elasticsearch.core.RequestFactory.toElasticsearchIndicesOptions(RequestFactory.java:1696)

The empty Option or WildcardState should be allowed, as for example the default STRICT_SINGLE_INDEX_NO_EXPAND_FORBID_CLOSED IndicesOption has an empty set of WildcardState and therefor fails if you use it.

I have a working fix (and test), will create a MR once i have resolved my upstream conflicts :D

[pnowak85]

backport to 4.3.x would be nice, as we are currently facing this issue in 4.3.1