allow components to return None

Author: rmorshea

src/idom/core/layout.py

@@ -203,7 +203,10 @@ def _render_component(
             # wrap the model in a fragment (i.e. tagName="") to ensure components have
             # a separate node in the model state tree. This could be removed if this
             # components are given a node in the tree some other way
-            raw_model = {"tagName": "", "children": [raw_model]}
+            raw_model = {
+                "tagName": "",
+                "children": [] if raw_model is None else [raw_model],
+            }
 
             self._render_model(old_state, new_state, raw_model)
         except Exception as error:

src/idom/core/proto.py

@@ -39,7 +39,7 @@ def definition_id(self) -> int:
         Usually the :func:`id` of this class or an underlying function.
         """
 
-    def render(self) -> VdomDict:
+    def render(self) -> VdomDict | ComponentType | None:
         """Render the component's :class:`VdomDict`."""