[monitoring-plugins] Fixed error message, added comment

[Bernd Arnold]

 Module: monitoring-plugins
 Branch: master
 Commit: 6a8564fb44ab6914dcc8ec63e8af6477803da080
 Author: Bernd Arnold <wopfel at gmail.com>
   Date: Sun Jun 17 09:42:25 2018 +0200
    URL: https://www.monitoring-plugins.org/repositories/monitoring-plugins/commit/?id=6a8564f

Fixed error message, added comment

---

 plugins-scripts/check_uptime.pl | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/plugins-scripts/check_uptime.pl b/plugins-scripts/check_uptime.pl
index ed859ab..4c9f22d 100755
--- a/plugins-scripts/check_uptime.pl
+++ b/plugins-scripts/check_uptime.pl
@@ -236,8 +236,9 @@ sub process_arguments(){
 		print "Upper Warning (-w) cannot be greater than Critical (-c)!\n";
 		exit $ERRORS{'UNKNOWN'};
 	}
+	# No "<=" since both values are zero if no range (only upper threshold values) is given
 	if ( $lower_warn_threshold < $lower_crit_threshold ) {
-		print "Lower Warning (-w) cannot be greater than Critical (-c)!\n";
+		print "Lower Warning (-w) cannot be less than Critical (-c)!\n";
 		exit $ERRORS{'UNKNOWN'};
 	}