pset.unshare_pset - fix bug where it would leaving an orphaned pset

It was leaving an orphaned pset if 'products' was a list of all elements pset is assigned to. Then it would create a new pset for each element leaving original pset orphaned.

src/ifcopenshell-python/test/api/pset/test_unshare_pset.py

@@ -69,6 +69,32 @@ class TestUnsharePset(test.bootstrap.IFC4):
 
         assert used_psets == set(psets)
 
+    def test_unshare_pset_for_all_pset_elements(self):
+        elements = [self.file.create_entity("IfcWall") for _ in range(3)]
+
+        pset = ifcopenshell.api.pset.add_pset(self.file, elements[0], "Foo")
+        pset_id = pset.id()
+        rel = self.file.by_type("IfcRelDefinesByProperties")[0]
+        rel.RelatedObjects = elements
+
+        new_psets = ifcopenshell.api.pset.unshare_pset(self.file, elements, pset)
+        # Original pset still exists and it's not orphaned.
+        pset = self.file.by_id(pset_id)
+
+        assert isinstance(new_psets, list)
+        assert len(new_psets) == 2
+
+        assert len(psets := self.file.by_type("IfcPropertySet")) == 3
+        assert len(self.file.by_type("IfcRelDefinesByProperties")) == 3
+
+        used_elements = set()
+        for pset in psets:
+            pset_elements = ifcopenshell.util.element.get_elements_by_pset(pset)
+            assert len(pset_elements) == 1
+            used_elements.update(pset_elements)
+
+        assert used_elements == set(elements)
+
 
 class TestUnsharePsetIFC2X3(test.bootstrap.IFC2X3, TestUnsharePset):
     pass