Modify tree validator (#430)

When a tree has multiple levels, it is possible that a top node has
"value" empty. That should be accepted.
Check for the validity of 'value' only if it's not empty, or if it's at
the last level of the tree hierarchy.

Author: margalva

src/ansys/dynamicreporting/core/utils/report_objects.py

@@ -1151,8 +1151,9 @@ def validate_tree(t):
                 raise ValueError("Tree payload dictionaries must have a 'value' key")
             if "children" in i:
                 ItemREST.validate_tree(i["children"])
-            # validate tree value
-            ItemREST.validate_tree_value(i["value"])
+            # validate tree value, only at the last level of the tree or if value is not empty
+            if len(i.get("children", [])) == 0 or (i.get("value") or "").strip():
+                ItemREST.validate_tree_value(i["value"])
 
     def set_payload_tree(self, t):
         self.validate_tree(t)