[WWcvs] webwork2: added check for $total==0 to eliminate potential DIV error

[Sam H. v. a. <we...@ma...>]

Log Message:
-----------
added check for $total==0 to eliminate potential DIV error (bug #855)

Modified Files:
--------------
    webwork2/lib/WeBWorK/ContentGenerator:
        Grades.pm

Revision Data
-------------
Index: Grades.pm
===================================================================
RCS file: /webwork/cvs/system/webwork2/lib/WeBWorK/ContentGenerator/Grades.pm,v
retrieving revision 1.18
retrieving revision 1.19
diff -Llib/WeBWorK/ContentGenerator/Grades.pm -Llib/WeBWorK/ContentGenerator/Grades.pm -u -r1.18 -r1.19
--- lib/WeBWorK/ContentGenerator/Grades.pm
+++ lib/WeBWorK/ContentGenerator/Grades.pm
@@ -337,7 +337,7 @@
 		
 
 		my $avg_num_attempts = ($num_of_problems) ? $num_of_attempts/$num_of_problems : 0;
-		my $successIndicator = ($avg_num_attempts) ? ($totalRight/$total)**2/$avg_num_attempts : 0 ;
+		my $successIndicator = ($avg_num_attempts && $total) ? ($totalRight/$total)**2/$avg_num_attempts : 0 ;
 	
 		push @rows, CGI::Tr(
 			CGI::td(CGI::a({-href=>$act_as_student_set_url}, WeBWorK::ContentGenerator::underscore2nbsp($setName))),