Turn value into a String before regex match (#2106)

Author: olleolleolle

Gemfile-rails-dependencies

@@ -1,5 +1,5 @@
 version_file = File.expand_path("../.rails-version", __FILE__)
-case version = ENV['RAILS_VERSION'] || (File.exist?(version_file) && File.read(version_file).chomp)
+case version = ENV['RAILS_VERSION'] || (File.exist?(version_file) && File.read(version_file).chomp) || ''
 when /master/
   gem "rails", :git => "https://github.com/rails/rails.git"
   gem "arel", :git => "https://github.com/rails/arel.git"