Fix(eos_designs): Address template values being None for custom template for ansible-core >= 2.19 (#6663)

Co-authored-by: Claus Holbech <holbech@arista.com>
Co-authored-by: Shivani-gslab <145646625+Shivani-gslab@users.noreply.github.com>

Author: 3 people

ansible_collections/arista/avd/extensions/molecule/ansible_only/custom_templates/empty.j2

@@ -0,0 +1,7 @@
+{# 
+  This template is used to test the output of custom template when the generated output is empty.
+  The behavior changed between ansible-core <2.19 and >=2.19
+#}
+{% if not_defined is arista.avd.defined %}
+{% endif %}
+

ansible_collections/arista/avd/extensions/molecule/ansible_only/inventory/group_vars/CUSTOM_TEMPLATES_SPINES.yml

@@ -12,3 +12,11 @@ spine:
     - name: custom-templates-spine1
       id: 1
       mgmt_ip: 192.168.200.101/24
+
+# Test custom template that produces empty output which behaves
+# differently in ansible-core <2.19 and ansible-core >=2.19
+eos_designs_custom_templates:
+  - template: custom_templates/empty.j2
+    options:
+      list_merge: append_rp
+      strip_empty_keys: false

ansible_collections/arista/avd/plugins/action/eos_designs_structured_config.py

@@ -125,6 +125,10 @@ def run(self, tmp: Any = None, task_vars: dict | None = None) -> dict:
                 # Here we parse the template, expecting the result to be a YAML formatted string
                 template_result = templater(template, template_vars, self.templar)
 
+                # Skip if template result is None or empty string
+                if not template_result:
+                    continue
+
                 # Load data from the template result.
                 template_result_data = yaml.safe_load(template_result)