Catch AttributeError in _prepare_yaml

of `orm.PortableCode`. Otherwise, the `_exportcontent` method of
`orm.Data` will fail, due to the discrepancy of the properties defined
in the pydantic model and what is actually being set as attributes of
the class.

src/aiida/orm/nodes/data/code/abstract.py

@@ -11,6 +11,7 @@
 from __future__ import annotations
 
 import abc
+import contextlib
 import functools
 import pathlib
 import typing as t
@@ -382,23 +383,24 @@ def get_builder(self) -> 'ProcessBuilder':
 
         return builder
 
-    def _prepare_yml(self, *args, **kwargs):
-        """Export code to a yml file."""
+    def _prepare_yaml(self, *args, **kwargs):
+        """Export code to a YAML file."""
         import yaml
 
         code_data = {}
         sort = kwargs.get('sort', False)
 
         for key in self.Model.model_fields.keys():
-            value = getattr(self, key).label if key == 'computer' else getattr(self, key)
+            with contextlib.suppress(AttributeError):
+                value = getattr(self, key).label if key == 'computer' else getattr(self, key)
 
-            # If the attribute is not set, for example ``with_mpi`` do not export it, so that there are no null-values
-            # in the resulting YAML file
-            if value is not None:
-                code_data[key] = str(value)
+                # If the attribute is not set, for example ``with_mpi`` do not export it
+                # so that there are no null-values in the resulting YAML file
+                if value is not None:
+                    code_data[key] = str(value)
 
         return yaml.dump(code_data, sort_keys=sort, encoding='utf-8'), {}
 
-    def _prepare_yaml(self, *args, **kwargs):
+    def _prepare_yml(self, *args, **kwargs):
         """Also allow for export as .yaml"""
-        return self._prepare_yml(*args, **kwargs)
+        return self._prepare_yaml(*args, **kwargs)