Little bug found

Hi!

Good plugin.
I found a little bug. Here is a patch for fixing it:
— ../check_snmp_environment.pl 2012-05-30 16:16:35.000000000 +0200
+++ ./check_snmp_environment.pl 2014-06-11 09:24:47.919573111 +0200
@@ -723,7 +723,7 @@

my $volt_global=0;
my %volt_status;
-if ($fanexist !=0) {
+if ($voltexist !=0) {
for ($i=0;$i