[WWcvs] pg: Fixed a typo in an error message.

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

Log Message:
-----------
Fixed a typo in an error message.

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

Revision Data
-------------
Index: Set.pm
===================================================================
RCS file: /webwork/cvs/system/pg/lib/Value/Set.pm,v
retrieving revision 1.3
retrieving revision 1.4
diff -Llib/Value/Set.pm -Llib/Value/Set.pm -u -r1.3 -r1.4
--- lib/Value/Set.pm
+++ lib/Value/Set.pm
@@ -39,7 +39,7 @@
     foreach my $x (@{$p}) {
       $x = Value::makeValue($x);
       $isFormula = 1 if Value::isFormula($x);
-      Value::Error("An element of sets can't be %s",Value::showClass($x))
+      Value::Error("An element of a set can't be %s",Value::showClass($x))
         unless Value::isRealNumber($x);
     }
   }