ext4: block_validity: Remove unnecessary ‘NULL’ values from new_node

new_node is assigned first, so it does not need to initialize the
assignment.

Signed-off-by: Li zeming <zeming@nfschina.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Link: https://patch.msgid.link/20240402022300.25858-1-zeming@nfschina.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>