can't get value from `plugin_redmine_chatwork`

[YasKaneda]

I have installed your plugin into our redmine(3.4.2.stable) and found an issue regarding plugin setting acquisition due to using hash/symbol.

I set debug logs in controller_issues_edit_after_save as follows:

plugin_redmine_chatwork = Setting.plugin_redmine_chatwork
post_updates_symbol = Setting.plugin_redmine_chatwork[:post_updates]
post_updates_subscript = Setting.plugin_redmine_chatwork["post_updates"]

Rails.logger.info("plugin_redmine_chatwork : #{plugin_redmine_chatwork}")
Rails.logger.info("post_updates_symbol : #{post_updates_symbol}")
Rails.logger.info("post_updates_subscript : #{post_updates_subscript}")

and I got result as follows:

plugin_redmine_chatwork : {"token"=>"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", "room"=>"https://kcw.kddi.ne.jp/#!rid99999999", "post_updates"=>"1", "post_wiki_updates"=>"1"}
post_updates_symbol : 
post_updates_subscript : 1

Could you please fix this so that we can obtain plugin_redmine_chatwork?

ref: https://github.com/sciyoshi/redmine-slack/blob/master/lib/redmine_slack/listener.rb#L35 https://github.com/sciyoshi/redmine-slack/blob/master/lib/redmine_slack/listener.rb#L47 https://github.com/sciyoshi/redmine-slack/blob/master/lib/redmine_slack/listener.rb#L108 https://github.com/sciyoshi/redmine-slack/blob/master/lib/redmine_slack/listener.rb#L206

[Sieg-Fried]

But, may not be able to read the value due to this correction. It's better to compare with 'nil' and verify the value. If value is 'nil', it's better to get value by the previous reference method.