fix: ignore unassigned hw-buttons

nspanel_blueprint.yaml

@@ -4999,6 +4999,8 @@ action:
       - conditions:
           - condition: trigger
             id: left_button_press
+          - condition: template
+            value_template: '{{ left_button_entity |length > 0 }}'  
         sequence:
           - service: >-
               {% if left_button_entity is match 'light.' %}
@@ -5050,6 +5052,8 @@ action:
       - conditions:
           - condition: trigger
             id: right_button_press
+          - condition: template
+            value_template: '{{ right_button_entity |length > 0 }}'
         sequence:
           - service: >-
               {% if right_button_entity is match 'light.' %}