Revision 1880374

Fix harmless uninitialized read in svn_fs_*_index_append

* subversion/libsvn_fs_fs/index.c (svn_fs_fs__l2p_index_append),
  subversion/libsvn_fs_x/index.c
  (svn_fs_x__l2p_index_append, svn_fs_x__p2l_index_append):
  Do not access entry fields that are unset due to reaching eof.

Found by: Clang 10 memory sanitizer

Patch by: Orivej Desh <orivej{_AT_}gmx.fr>

Reviewed by: danielsh (svn_fs_fs__l2p_index_append)
             hartmannathan