fix: 修复formats的逻辑

lib/tallty_import_export/export_form.rb

@@ -89,7 +89,7 @@ module TalltyImportExport
                   row << nil
                 end
                 formats.push(
-                  header_obj.flatten_value[col_index].format&.to_sym || row.last.is_a?(String) ? :string : nil
+                  header_obj.flatten_value[col_index].format&.to_sym || (row.last.is_a?(String) ? :string : nil)
                 )
               end
               sheet.add_row(row, style: title3, height: @row_height, types: formats)