Handle undef and empty LocalAddr

IO::Socket::INET interprets undefined and empty string LocalAddr
arguments as an unspecified address while IO::Socket::IP returns an
error. This seems to be one of the differences between the two
Socket implementations. Recent IO::Socket::IP (0.39) accepts undefined
value, but still bail outs on an empty string:

$ perl -Ilib -MHTTP::Daemon -e '$d=HTTP::Daemon->new(LocalAddr=>undef) or die; print $d->url, qq{\n}'
http://fedora-31:42587/
$ perl -Ilib -MHTTP::Daemon -e '$d=HTTP::Daemon->new(LocalAddr=>q{}) or die; print $d->url, qq{\n}'
Name or service not known       ...propagated at -e line 1.

To improve compatibility, this patch adds a special handling for these
two values to be accepted as an unspecified value. Though this should
be corrected on IO::Socket:IP side probably.

CPAN RT#91699
CPAN RT#123069

Signed-off-by: Petr Písař <ppisar@redhat.com>

Author: ppisar

Changes

@@ -1,6 +1,8 @@
 Revision history for HTTP-Daemon
 
 {{$NEXT}}
+  - Handle undef and empty LocalAddr value in new() constructor as an
+    unspecified address (GH#24, RT#123069)
 
 6.05      2019-07-26 20:41:05Z
   - Added the .perltidyrc from the libwww-perl distribution

lib/HTTP/Daemon.pm

@@ -22,6 +22,14 @@ sub new {
     my ($class, %args) = @_;
     $args{Listen} ||= 5;
     $args{Proto}  ||= 'tcp';
+
+    # Handle undefined or empty local address the same way as
+    # IO::Socket::INET -- use unspecified address
+    for my $key (qw(LocalAddr LocalHost)) {
+        if (exists $args{$key} && (!defined $args{$key} || $args{$key} eq '')) {
+            delete $args{$key};
+        }
+    }
     return $class->SUPER::new(%args);
 }