Make sure codecForLocale returns a valid codec in bootstrap mode

This was a regression caused by acbfb4d777,
causing for instance qdoc to crash.

Change-Id: Id8daa19d467c4f1729e5a5a203a388f16ec4a6de
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

src/corelib/codecs/qtextcodec.cpp

@@ -249,10 +249,10 @@ static QTextCodec *setupLocaleMapper()
             locale = checkForCodec("ISO 8859-15");
     }
 
+#endif
     // If everything failed, we default to 8859-1
     if (!locale)
         locale = QTextCodec::codecForName("ISO 8859-1");
-#endif
     globalData->codecForLocale.storeRelease(locale);
     return locale;
 }