Using https://github.com/WordPress/gutenberg/commit/5e0b80a4496bba1671f983dd1e89c2fe93c7dbd7 I'm seeing two PHP notices when creating a new post: <img width="1306" alt="php-notices" src="https://user-images.githubusercontent.com/617637/85200338-e7dde780-b2f6-11ea-85f8-f17b5b0fa5ba.png"> The PHP notices are not there if the Gutenberg plugin is disabled so might be something that has recently changed and could land in core soon.