[WWcvs] pg: Clear the error message before checking the student's answer for errors.

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

Log Message:
-----------
Clear the error message before checking the student's answer for errors.

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 1.121
retrieving revision 1.122
diff -Llib/Value/AnswerChecker.pm -Llib/Value/AnswerChecker.pm -u -r1.121 -r1.122
--- lib/Value/AnswerChecker.pm
+++ lib/Value/AnswerChecker.pm
@@ -1686,6 +1686,7 @@
 sub cmp_postprocess {
   my $self = shift; my $ans = shift;
   return unless $ans->{score} == 0;
+  $self->{context}->clearError;
   eval {$ans->{student_formula}->reduce} if defined($ans->{student_formula}); # check for bad function calls
   $self->cmp_error($ans) if $self->{context}{error}{flag};                    #  and report the error
   return if $ans->{ans_message} || $ans->{isPreview};