Mention that an empty password is the same as no password.

man/zip_fopen_encrypted.mdoc

diff --git a/man/zip_fopen_encrypted.mdoc b/man/zip_fopen_encrypted.mdoc
index 58319e1..f40cc7c 100644
--- a/man/zip_fopen_encrypted.mdoc
+++ b/man/zip_fopen_encrypted.mdoc
@@ -29,7 +29,7 @@
 .\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 .\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd September 14, 2020
+.Dd September 15, 2020
 .Dt ZIP_FOPEN_ENCRYPTED 3
 .Os
 .Sh NAME
@@ -54,6 +54,12 @@
 using the password given in the
 .Ar password
 argument.
+If
+.Ar password
+is
+.Dv NULL
+or the empty string, the default password is used (see
+.Xr zip_set_default_password 3 ) .
 The
 .Ar flags
 argument are the same as for

man/zip_set_default_password.mdoc

diff --git a/man/zip_set_default_password.mdoc b/man/zip_set_default_password.mdoc
index 79fb0ca..855c632 100644
--- a/man/zip_set_default_password.mdoc
+++ b/man/zip_set_default_password.mdoc
@@ -29,7 +29,7 @@
 .\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 .\" IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd September 14, 2020
+.Dd September 15, 2020
 .Dt ZIP_SET_DEFAULT_PASSWORD 3
 .Os
 .Sh NAME
@@ -48,8 +48,8 @@
 If
 .Ar password
 is
-.Dv NULL ,
-the default password is unset.
+.Dv NULL
+or the empty string, the default password is unset.
 .Pp
 If you prefer a different password for single files, use
 .Xr zip_fopen_encrypted 3