[WWcvs] pg: Since $self->{tree} is not inherited, cache it beforehand so that we can use it afterward.

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

Log Message:
-----------
Since $self->{tree} is not inherited, cache it beforehand so that we
can use it afterward.

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

Revision Data
-------------
Index: Formula.pm
===================================================================
RCS file: /webwork/cvs/system/pg/lib/Value/Formula.pm,v
retrieving revision 1.66
retrieving revision 1.67
diff -Llib/Value/Formula.pm -Llib/Value/Formula.pm -u -r1.66 -r1.67
--- lib/Value/Formula.pm
+++ lib/Value/Formula.pm
@@ -224,9 +224,9 @@
 #  (so it's nodes point to the correct equation, for one thing)
 #
 sub inherit {
-  my $self = shift;
+  my $self = shift; my $tree = $self->{tree};
   $self = $self->SUPER::inherit(@_);
-  $self->{tree} = $self->{tree}->copy($self);
+  $self->{tree} = $tree->copy($self);
   return $self;
 }