silence warning with GCC -Wextra

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@55400 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -721,7 +721,9 @@ private:
       // used for length caching only so far, i.e. it doesn't count as a hit
       // from our point of view
       if ( cache->pos )
+      {
           wxCACHE_PROFILE_FIELD_INC(poshits);
+      }
 
       if ( pos == cache->pos )
           return cache->impl;