Early return when token_stream is nil

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>

Author: 2 people

lib/rdoc/token_stream.rb

@@ -112,7 +112,7 @@ def token_stream
   # Returns a string representation of the token stream
 
   def tokens_to_s
-    Array(token_stream).compact.map { |token| token[:text] }.join ''
+    (token_stream or return '').compact.map { |token| token[:text] }.join ''
   end
 
 end