Fixed an issue with IOSource#read_until when reaching the end of a file

[naitoh]

Fix GH-287

Why?

If @source = nil is set at the end of the file, prevent IOSource#read_until from raising an error.

/.gems/gems/rexml-3.4.2/lib/rexml/parsers/baseparser.rb:524:in 'REXML::Parsers::BaseParser#pull_event': #<NoMethodError: undefined method 'eof?' for nil> (REXML::ParseException)
.gems/gems/rexml-3.4.2/lib/rexml/source.rb:275:in 'REXML::IOSource#read_until'

rexml/lib/rexml/source.rb

Lines 266 to 276 in 185bdc7

	def read_until(term)
	pattern = Private::PRE_DEFINED_TERM_PATTERNS[term] || /#{Regexp.escape(term)}/
	term = @encoded_terms[term] ||= encode(term)
	until str = @scanner.scan_until(pattern)
	break if @source.nil?
	break if @source.eof?
	@scanner << readline(term)
	end
	if str
	read if @scanner.eos? and !@source.eof?
	str

1. Reaching the end of a file in IOSource#read.
2. If the string remains in @scanner.rest, use @scanner.scan_until(pattern) to return str.
3. If @source is nil, an exception occurs.

[kou]

Thanks.