reindexing models on an ES cluster that is totally new / empty throws the following exception:
reindexing models on an ES cluster that is totally new / empty throws the following exception:

irb(main):001:0> User.reindex

NoMethodError: undefined method `keys' for []:Array
	from /app/vendor/bundle/ruby/2.1.0/gems/searchkick-1.2.1/lib/searchkick/index.rb:151:in `clean_indices'
	from /app/vendor/bundle/ruby/2.1.0/gems/searchkick-1.2.1/lib/searchkick/index.rb:163:in `reindex_scope'
	from /app/vendor/bundle/ruby/2.1.0/gems/searchkick-1.2.1/lib/searchkick/model.rb:51:in `searchkick_reindex'
	from (irb):1
	from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.0.4/lib/rails/commands/console.rb:90:in `start'
	from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.0.4/lib/rails/commands/console.rb:9:in `start'
	from /app/vendor/bundle/ruby/2.1.0/gems/railties-4.0.4/lib/rails/commands.rb:62:in `<top (required)>'
	from bin/rails:4:in `require'
	from bin/rails:4:in `<main>'

When I looked into it, client.indices.get_alias returns a hash, not an array, so the NotFound rescue should be returning an empty hash.  This change fixes the issue.

I did NOT add a unit test because the only way to test this would be to either nuke all indexes from the local ES test cluster, or startup a totally vanilla cluster just for running the test, which is kind of out of the scope of this change.

st0012/searchkick,savayg/searchkick,johan--/searchkick,klebervirgilio/searchkick,ankane/searchkick,bukalapak/searchkick,mikelkew/searchkick,bukalapak/searchkick,meetrajesh/searchkick,instacart/searchkick,johan--/searchkick,meetrajesh/searchkick,Xtinct/searchkick,instacart/searchkick,savayg/searchkick,elguapo1611/searchkick,klebervirgilio/searchkick,elguapo1611/searchkick,mikelkew/searchkick,spanner/searchkick,jprosevear/searchkick,spanner/searchkick,st0012/searchkick,Xtinct/searchkick,jprosevear/searchkick