Update flatten.py

flatten.py

@@ -7,7 +7,9 @@ from specklepy.objects import Base
 
 def flatten_base(base: Base) -> Iterable[Base]:
     """Take a base and flatten it to an iterable of bases."""
-    if hasattr(base, "elements"):
-        for element in base["elements"]:
-            yield from flatten_base(element)
+    if hasattr(base, "elements") and base.elements is not None:
+        # Check if base.elements is not only present and non-None, but also an iterable
+        if isinstance(base.elements, Iterable):
+            for element in base.elements:
+                yield from flatten_base(element)
     yield base