Problem:
b98eefd added `!b_p_bl` to `ignore_buf()`, which also
skips bdelete'd buffers since bdelete unsets `b_p_bl`.
Solution:
Check `b_p_initialized` together with `b_p_bl` so that
bdelete'd buffers (which have b_p_initialized=false) are not
filtered out. Keep `b_p_bl` check only in `shada_get_buflist()`.
(cherry picked from commit 496374e951)
915880d252