my $uri = URI->new($ENV{'REQUEST_URI'});
my %query = $uri->query_form;
-my $origin = lc $query{'origin'}; # lower case
-my $graph = $query{'graph'};
-my $range = lc $query{'range'}; # lower case
+my $origin = lc ($query{'origin'} // ''); # lower case
+my $graph = $query{'graph'} // '';
+my $range = lc ($query{'range'} // ''); # lower case
# Check parameters
unless(($origin =~ /^\w+?\.cgi$/) && ($graph =~ /^[\w\-.,; ]+?$/) && ($range ~~ @Graphs::time_ranges)) {