save year value by writing conference's period_start_date or year

lib/tasks/sync_ntnu_personal_data_tasks.rake

@@ -106,6 +106,7 @@ def sync_conference_papers(query_result, user)
     wc = WritingConference.new
     apa_title = nil
     invalid_apa_title = [nil, '', '必填欄位', '無', 'n/a', 'non']
+    invalid_values = [nil, '', '必填欄位', '無', 'n/a', 'non']
 
     j_data['data'].each do |data|
       case data['eifSn']
@@ -125,7 +126,6 @@ def sync_conference_papers(query_result, user)
         temp_date = Date.strptime(data['data'].first['v'], '%Y/%m/%d') rescue nil
         if temp_date.nil?
           wc.period_start_date = nil
-          wc.year = nil
         else
           wc.period_start_date = temp_date
           wc.year = temp_date.year
@@ -134,6 +134,10 @@ def sync_conference_papers(query_result, user)
         wc.period_end_date = data['data'].first['v']
         #when '20190109101534767' # 合著之國際學者姓名與機構
         #  wc.authors = data['data'].first['v']
+      when '20190109103134500' # 會議年份
+        if !invalid_values.include? data['data'].first['v']
+          wc.year = data['data'].first['v']
+        end
       when '20140313173831962' # 完整引文內容
         apa_title = data['data'].first['v']
       else