Handle empty rows

lib/blazer/adapters/athena_adapter.rb

@@ -55,7 +55,7 @@ module Blazer
 
             utc = ActiveSupport::TimeZone['Etc/UTC']
 
-            rows = untyped_rows[1..-1]
+            rows = untyped_rows[1..-1] || []
             column_types.each_with_index do |ct, i|
               # TODO more column_types
               case ct