Improve support for 'empty' parentheses

When the user uses "parens => ''" in format_list.

lib/DDG/GoodieRole/Parse/List.pm

@@ -107,6 +107,10 @@ sub format_list {
     my $parens = $options{parens} // '[]';
     @parens = ref $parens eq 'ARRAY'
         ? @$parens : split '', $parens;
+    # In the case the user uses parens => '' we don't want to
+    # display *any* parentheses, so we need to have 'fake'
+    # parentheses.
+    @parens = ('', '') if "@parens" eq '';
     return $parens[0] .  join(', ', map {
         ref $_ eq 'ARRAY' ? format_list($_, %options) : $_
     } @$items) . $parens[$#parens];

t/00-roles/Parse/List.t

@@ -188,6 +188,10 @@ subtest format_list => sub {
                 [1, 2, 3]   => '{1, 2, 3}',
                 [1, [2, 3]] => '{1, {2, 3}}',
             ],
+            '' => [
+                [1, 2, 3]   => '1, 2, 3',
+                [1, [2, 3]] => '1, 2, 3',
+            ],
         );
         foreach (pairs @tcs) {
             my ($parens, $cases) = @$_;