feat: add find_each for association_records

lib/tallty_import_export/export.rb

@@ -125,12 +125,16 @@ module TalltyImportExport
         first_content_row_index = respond_to?(:first_header) ? 2 : 1
 
         index = 0
-        association_records.each do |association_record|
+        # 如果 association_records 是 ActiveRecord::Relation 对象，使用 find_each 进行批量处理，否则使用 each
+        record_each_method = association_records.is_a?(ActiveRecord::Relation) ? :find_each : :each
+        association_records.send(record_each_method) do |association_record|
           records = @each_method.present? ?
             (try_method(association_record, @each_method) || [nil]) :
             [association_record]
 
-          records.each do |record|
+          records.compact.each do |record|
+            next if record.nil?
+
             record.ta_statistics = record.ta_statistic(options[:resource_stat_condition]) if options[:resource_stat_condition].present?
 
             row = []
@@ -158,6 +162,7 @@ module TalltyImportExport
             last_row = row
           end
         end
+
         # 需要根据column进行多行的内容合并
         if merge_column_hash.present?
           merge_column_hash.each do |col_index, row_arr|