add check for undefined variables

tasks/main.yml

@@ -4,6 +4,7 @@
     name: "{{ item.groups }}"
     state: present
   with_items: "{{ human_users }}"
+  when: ( item.groups is defined )
   become: true
 
 - name: Make sure extra groups exist
@@ -11,6 +12,7 @@
     name: "{{ item.extra_groups }}"
     state: present
   with_items: "{{ human_users }}"
+  when: ( item.extra_groups is defined )
   become: true
 
 - name: Create user accounts
@@ -36,6 +38,7 @@
     groups: "{{ item.extra_groups }}"
     append: true
   with_items: "{{ human_users }}"
+  when: ( item.extra_groups is defined )
   become: true
 
 - name: Delete absent user accounts