small rtruncate refactoring

lib/ext/core/string.rb

@@ -24,13 +24,13 @@ class String
 
   # same as reverse.truncate.reverse
   def rtruncate(length, options = {})
-    text = self.dup
+    chars = self.dup.mb_chars
+    return self if chars.length <= length
     options[:omission] ||= "..."
     options[:separator] ||= '/'
 
-    chars = text.mb_chars
     start = chars.length - length + options[:omission].mb_chars.length
     stop = options[:separator] ? (chars.index(options[:separator].mb_chars, start) || start) : start
-    (chars.length > length ? "#{options[:omission]}#{chars[stop..-1]}" : text).to_s
+    "#{options[:omission]}#{chars[stop..-1]}".to_s
   end
 end