corrected a warning prevention condition

app/models/chunks/wiki.rb

@@ -70,7 +70,7 @@ module WikiChunk
   # method will return the WikiWord instead of the usual +nil+.
   # The +page_name+ method returns the matched WikiWord.
   class Word < WikiLink
-    unless defined? WIKI_LINK
+    unless defined? WIKI_WORD
       WIKI_WORD = Regexp.new('(":)?(\\\\)?(' + WikiWords::WIKI_WORD_PATTERN + ')\b', 0, "utf-8")
     end