collectd: sqm_collectd: improve error handling

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>
(cherry picked from commit 947c85bff0)

utils/collectd/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=collectd
 PKG_VERSION:=5.11.0
-PKG_RELEASE:=5
+PKG_RELEASE:=6
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
 PKG_SOURCE_URL:=https://collectd.org/files/ \

utils/collectd/files/exec-scripts/sqm_collectd.sh

@@ -80,6 +80,8 @@ process_qdisc() {
 
 	ifc="$1"
 	jsn=$(tc -s -j qdisc show dev "$ifc")
+	[ $? ] || return
+
 	# strip leading & trailing []
 	jsn="${jsn#[}" ; jsn="${jsn%]}"