Updated the getattr patch (#699)

# Description
Ensure that we can access annotations added by imported ontologies.

This issue was revealed when running the periodictable script for EMMO
1.0.0-beta5.

## Type of change
- [x] Bug fix.
- [ ] New feature.
- [ ] Documentation update.
- [ ] Test update.

## Checklist
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after creating the PR. -->

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- [ ] Is the code easy to read and understand?
- [ ] Are comments for humans to read, not computers to disregard?
- [ ] Does a new feature has an accompanying new test (in the CI or unit
testing schemes)?
- [ ] Has the documentation been updated as necessary?
- [ ] Does this close the issue?
- [ ] Is the change limited to the issue?
- [ ] Are errors handled for all outcomes?
- [ ] Does the new feature provide new restrictions on dependencies, and
if so is this documented?

## Comments
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applicable. -->

Co-authored-by: Francesca L. Bleken <48128015+francescalb@users.noreply.github.com>

ontopy/patch.py

@@ -29,6 +29,7 @@ def render_func(entity):
 # Extending ThingClass (classes)
 # ==============================
 
+# Save a copy of the unpatched ThingClass.__getattr__() method.
 save_getattr = ThingClass.__getattr__
 
 
@@ -133,7 +134,13 @@ def _getattr(self, name):
             entity = self.namespace.ontology.get_by_label(name)
             # add annotation property to world._props for faster access later
             self.namespace.world._props[name] = entity
-            return save_getattr(self, entity.name)
+
+            # Try first unpatched getattr method to avoid risking
+            # infinite recursion.
+            try:
+                return save_getattr(self, entity.name)
+            except AttributeError:
+                return getattr(self, entity.name)
         raise err