[WWcvs] pg: Don't do equivalence check if prefilters are erased

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

Log Message:
-----------
Don't do equivalence check if prefilters are erased

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 1.124
retrieving revision 1.125
diff -Llib/Value/AnswerChecker.pm -Llib/Value/AnswerChecker.pm -u -r1.124 -r1.125
--- lib/Value/AnswerChecker.pm
+++ lib/Value/AnswerChecker.pm
@@ -1648,6 +1648,7 @@
   my $self = shift; my $ans = shift;
   $ans->{_filter_name} = "produce_equivalence_message";
   return $ans if $ans->{ans_message}; # don't overwrite other messages
+  return $ans unless defined($ans->{prev_ans}); # if prefilters are erased, don't do this check
   my $context = $self->context;
   $ans->{prev_formula} = Parser::Formula($context,$ans->{prev_ans});
   if (defined($ans->{prev_formula}) && defined($ans->{student_formula})) {