Author: Alexander Zangerl <az@debian.org>
Subject: fixes match_forall wrt. nonexistent super/subclass assocs

--- a/lib/TM.pm
+++ b/lib/TM.pm
@@ -3059,8 +3059,8 @@ sub is_subclass {
     # if we still do not have a decision, we will check all super types of $class and see (recursively) whether we can establish is-subclass-of
     return 1 if grep ($self->is_subclass ($_, $super),                       # check all of the intermediate type whether there is a transitive relation
 		      map { $self->get_x_players ($_, $SUPERCLASS) }         # find the superclass player there => intermediate type
-		      $self->match_forall (type       => $SUBCLASSES,
-					   subclass   => $class)
+		      grep(defined $_,$self->match_forall (type       => $SUBCLASSES,
+							   subclass   => $class))
 		      );
     return 0;                                                                # ok, we give up now
 }