Move snippet_viewset assignment to SnippetViewSet.on_register()

wagtail/snippets/models.py

@@ -97,7 +97,6 @@ def _register_snippet_immediately(model, viewset=None):
 
     admin_viewset = viewset(model)
     viewsets.register(admin_viewset)
-    model.snippet_viewset = admin_viewset
 
     SNIPPET_MODELS.append(model)
     SNIPPET_MODELS.sort(key=lambda x: x._meta.verbose_name)

wagtail/snippets/views/snippets.py

@@ -1371,5 +1371,8 @@ class SnippetViewSet(ModelViewSet):
 
     def on_register(self):
         super().on_register()
+        # For convenience, attach viewset to the model class to allow accessing
+        # the configuration of a given model.
+        self.model.snippet_viewset = self
         viewsets.register(self.chooser_viewset)
         self.register_model_check()