org项目导出为markdown失败，怎么回事

闲聊灌水
1

这是我的 org-publish-project-alist，仿照网上的教程写的

	  org-publish-project-alist '(
				      ("images"
				       :base-directory "~/ChiniBlogs/src/"
				       :base-extension "jpg\\|png\\|gif"
				       :publishing-directory "~/ChiniBlogs/html"
				       :recursive t
				       :publishing-function org-publish-attachment)
				      ("static"
				       :base-directory "~/ChiniBlogs/static"
				       :base-extension "jpg\\|png\\|gif\\|css\\|js"
				       :publishing-directory "~/ChiniBlogs/html/static"
				       :recursive t
				       :publishing-function org-publish-attachment)
				      ("wiki-html"
				       :base-directory "~/ChiniBlogs/src/"
				       :base-extension "org"
				       :publishing-directory "~/ChiniBlogs/html"
				       :html-head "<link rel=\"stylesheet\" type=\"text/css\" href=\"http://gongzhitaao.org/orgcss/org.css\"/>"
				       :recursive t
				       :publishing-function org-html-publish-to-html
				       :auto-preamble t
				       :section-numbers nil
				       :author "Steiner"
				       :headline-levels 4)

然后，我依葫芦画瓢，设置了几个导出为markdown, pdf的配置

				      ("wiki-markdown"
				       :base-directory "~/ChiniBlogs/src/"
				       :base-extension "org"
				       :publishing-directory "~/ChiniBlogs/markdown"
				       :html-head "<link rel=\"stylesheet\" type=\"text/css\" href=\"http://gongzhitaao.org/orgcss/org.css\"/>"
				       :recursive t
				       :publishing-function org-md-export-to-markdown
				       :auto-preamble t
				       :section-numbers nil
				       :author "Steiner"
				       :headline-levels 4)

这里 markdown 的导出配置没有贴出来，他的配置与markdown类似，出的问题的跟其一样 都是 Unknown "nil" back-end: Aborting export
就一个wiki-html项目导出没有事，wiki-markdown有问题，但是单独使用org-md-export-to-markdown的时候又没问题，实在搞不懂怎么回事