watchcat: set default value for mmifacename to prevent argument shift

Set mmifacename default to "null" instead of an empty string to avoid
argument displacement when the value is not defined. Also remove leftover
debug comments from previous commit.

Signed-off-by: Ivan Diaz <diaz.it@icloud.com>

Author: Ivan Diaz

utils/watchcat/files/watchcat.init

@@ -38,8 +38,8 @@ config_watchcat() {
 	config_get pingperiod "$1" pingperiod "60"
 	config_get forcedelay "$1" forcedelay "60"
 	config_get pingsize "$1" pingsize "standard"
-	config_get interface "$1" interface # CHEK only if need a default?
-	config_get mmifacename "$1" mmifacename # FIX HERE need a default?
+	config_get interface "$1" interface
+	config_get mmifacename "$1" mmifacename "null"
 	config_get_bool unlockbands "$1" unlockbands "0"
 	config_get addressfamily "$1" addressfamily "any"
 	config_get script "$1" script
@@ -73,7 +73,7 @@ config_watchcat() {
 				append_string "warn" "pingperiod cannot be a negative value." "; "
 			fi
 
-			if [ "$mmifacename" != "" ] && [ "$period" -lt 30 ]; then
+			if [ "$mmifacename" != "null" ] && [ "$period" -lt 30 ]; then
 				append_string "error" "Check interval is less than 30s. For robust operation with ModemManager modem interfaces it is recommended to set the period to at least 30s."
 			fi
 		fi