Check that AnsibleUndefinedVariable doesn't occur when an unused variable references an undefined variable (#35571)

* Check that AnsibleUndefinedVariable doesn't occur

* AnsibleUndefinedVariable exc.: don't modify type

test/integration/targets/template/runme.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+set -eux
+
+ANSIBLE_ROLES_PATH=../ ansible-playbook template.yml -i ../../inventory -e @../../integration_config.yml -v "$@"
+
+# Test for #35571
+ansible testhost -i testhost, -m debug -a 'msg={{ hostvars["localhost"] }}' -e "vars1={{ undef }}" -e "vars2={{ vars1 }}"

test/integration/targets/template/template.yml

@@ -0,0 +1,4 @@
+- hosts: testhost
+  gather_facts: yes
+  roles:
+    - { role: template }