base-files: Fix config_generate when there are no switch VLANs or ports configured in board.json.

The json_select call fails when there are no roles or ports objects in board.json. "json_select .." must not be executed after failing.

This fixes for example LEDs not being set up in /etc/config/system.

Signed-off-by: Vittorio Gambaletta <openwrt@vittgam.net>

package/base-files/files/bin/config_generate

@@ -143,6 +143,7 @@ generate_switch_vlans_ports() {
 	# autogenerate vlans
 	#
 
+	if json_is_a roles array; then
 		json_get_keys roles roles
 		json_select roles
 
@@ -160,12 +161,14 @@ generate_switch_vlans_ports() {
 		done
 
 		json_select ..
+	fi
 
 
 	#
 	# write port specific settings
 	#
 
+	if json_is_a ports array; then
 		json_get_keys ports ports
 		json_select ports
 
@@ -192,6 +195,7 @@ generate_switch_vlans_ports() {
 		done
 
 		json_select ..
+	fi
 }
 
 generate_switch() {