fix minor bug with nowiki tag

Thanks User:Protnet for report and User:Phorgo for help.

http://www.mediawiki.org/wiki/Extension_talk:MagicNoCache#Minor_bug_with_nowiki_tag_31305

Change-Id: Ia80c5cb0bf9a89c16d8ee00dd770b71a2d5975c4
(cherry picked from commit 4e67cebe27cdbbcdf88ca44220622bf8528f8747)