Metasploitが起動しないので gem updateしたらrubyがエラーになった

Bundler could not find compatible versions for gem "activerecord":
  In Gemfile:
    metasploit-framework-db was resolved to 4.11.0.pre.dev, which depends on
    metasploit_data_models (= 0.24.0) was resolved to 0.24.0, which depends on
    arel-helpers was resolved to 2.1.1, which depends on
      activerecord (= 4.0.13)

    metasploit-framework-db was resolved to 4.11.0.pre.dev, which depends on
	activerecord (< 4.0.0, >= 3.2.21)

    metasploit-framework-db was resolved to 4.11.0.pre.dev, which depends on
	metasploit_data_models (= 0.24.0) was resolved to 0.24.0, which depends on
	activerecord (< 4.0.0, >= 3.2.13)

sudo gem update
ERROR:  While executing gem ... (RDoc::Error)
    error generating
    /usr/local/lib/ruby/gems/2.1/doc/nokogiri-1.6.7.1/rdoc/Rakefile.html:
    Error while evaluating
    /usr/local/lib/ruby/gems/2.1/gems/rdoc-3.12.2/lib/rdoc/generator/template/darkfish/page.rhtml:
    undefined method `chomp' for nil:NilClass (RDoc::Error)