[WWcvs] pg: Make sure Formula's value() method doesn't produce an error when it can't extact the separate entries of the formula.

[dpvc v. a. <we...@ma...>]

Log Message:
-----------
Make sure Formula's value() method doesn't produce an error when it
can't extact the separate entries of the formula.

Modified Files:
--------------
    pg/lib/Value:
        AnswerChecker.pm

Revision Data
-------------
Index: AnswerChecker.pm
===================================================================
RCS file: /webwork/cvs/system/pg/lib/Value/AnswerChecker.pm,v
retrieving revision 1.110
retrieving revision 1.111
diff -Llib/Value/AnswerChecker.pm -Llib/Value/AnswerChecker.pm -u -r1.110 -r1.111
--- lib/Value/AnswerChecker.pm
+++ lib/Value/AnswerChecker.pm
@@ -1988,6 +1988,7 @@
 #
 sub value {
   my $self = shift;
+  return $self unless defined $self->{tree}{coords};
   my $context = $self->context;
   my @array = ();
   if ($self->{tree}->type eq 'Matrix') {