share/rbbt_commands/tsv/attach in rbbt-util-5.21.51 vs share/rbbt_commands/tsv/attach in rbbt-util-5.21.53

@@ -37,9 +37,10 @@
 end
 
 fields = fields ? fields.split(/[,|]/).collect{|f| f.strip} : nil
 
 tsv = TSV.open(file1, :unnamed => true)
+tsv = tsv.to_double if tsv.type == :flat
 
 rest.each do |file2|
   file_fields = TSV.parse_header(file2).all_fields - tsv.all_fields
   these_fields = fields ? fields & file_fields : nil
   tsv = tsv.attach file2, :fields => these_fields, :identifiers => identifiers