"Handle" fetching the resource of a volume action

doapi/action.py

@@ -106,12 +106,16 @@ def fetch_resource(self):
         """
         Fetch & return the resource that the action operated on, or `None` if
         the resource no longer exists (specifically, if the API returns a 404)
+        or no resource is given (specifically, if the `resource_id` field is
+        `None`, which is the case for actions on volumes)
 
         :rtype: `Droplet`, `Image`, `FloatingIP`, or `None`
         :raises ValueError: if the action has an unknown ``resource_type``
             (This indicates a deficiency in the library; please report it!)
         :raises DOAPIError: if the API endpoint replies with a non-404 error
         """
+        if self.get("resource_id") is None:
+            return None
         try:
             if self.resource_type == "droplet":
                 return self.doapi_manager.fetch_droplet(self.resource_id)