Addapt default encoding in SQL Server

Author: kitsuyui

app/models/table_memo_raw_dataset_column.rb

@@ -9,7 +9,8 @@ def format_value(value)
       when 'timestamp'
         '0x' + value.unpack('H*')[0]
       else
-        value.to_s.encode(Encoding.default_internal, datasource_encoding).gsub(/\u0000/, '')
+        dst_enc = Encoding.default_internal or 'UTF-8'
+        value.to_s.encode(dst_enc, datasource_encoding).gsub(/\u0000/, '')
       end
     else
       case sql_type