Bug Fixing : Could not add new undefined tag if searchfield>0

For instance, search for tag 290
cannot find.
Click on addTag
Save
Then wouldnot add tag 290 because used UPDATE.
Now, if tag is not found then Add tag is done.

Signed-off-by: Chris Cormack <crc@liblime.com>
Signed-off-by: Joshua Ferraro <jmf@liblime.com>

admin/marctagstructure.pl

@@ -123,9 +123,9 @@ if ($op eq 'add_form') {
 			-default => $data->{'authorised_value'},
 			);
 
-	if ($searchfield) {
-		$template->param(action => "Modify tag",
-								searchfield => $searchfield);
+  $template->param(searchfield => $searchfield) if ($searchfield);
+	if ($data eq undef) {
+		$template->param(action => "Modify tag");
 		$template->param('heading-modify-tag-p' => 1);
 	} else {
 		$template->param(action => "Add tag");