Comment 3 for bug 1641612

In file included from /home/laurynas/mysql-server/storage/innobase/include/btr0btr.h:29:0,
                 from /home/laurynas/mysql-server/storage/innobase/btr/btr0btr.c:26:
/home/laurynas/mysql-server/storage/innobase/btr/btr0btr.c: In function 'dict_index_is_ibuf':
/home/laurynas/mysql-server/storage/innobase/include/ut0dbg.h:37:42: warning: nonnull argument 'index' compared to NULL [-Wnonnull-compare]
 # define UT_DBG_FAIL(EXPR) UNIV_UNLIKELY(!((ulint)(EXPR)))
                                          ^~~~~~~~~~~~~~~~
/home/laurynas/mysql-server/storage/innobase/include/univ.i:459:54: note: in definition of macro 'UNIV_EXPECT'
 # define UNIV_EXPECT(expr,constant) __builtin_expect(expr, constant)
                                                      ^~~~
/home/laurynas/mysql-server/storage/innobase/include/ut0dbg.h:37:28: note: in expansion of macro 'UNIV_UNLIKELY'
 # define UT_DBG_FAIL(EXPR) UNIV_UNLIKELY(!((ulint)(EXPR)))
                            ^~~~~~~~~~~~~
/home/laurynas/mysql-server/storage/innobase/include/ut0dbg.h:64:6: note: in expansion of macro 'UT_DBG_FAIL'
  if (UT_DBG_FAIL(EXPR)) { \
      ^~~~~~~~~~~
/home/laurynas/mysql-server/storage/innobase/include/ut0dbg.h:79:21: note: in expansion of macro 'ut_a'
 #define ut_ad(EXPR) ut_a(EXPR)
                     ^~~~
/home/laurynas/mysql-server/storage/innobase/include/dict0dict.ic:279:2: note: in expansion of macro 'ut_ad'
  ut_ad(index);
  ^~~~~