Ensure that the context terms are defined when run

[moisbo]

Add Ensure Context like in crate-o.

https://github.com/Language-Research-Technology/crate-o/blob/c3716debd56a60cac60639926c9b018ab5c3163d/src/components/EditorState.js#L290

https://github.com/Language-Research-Technology/crate-o/blob/c3716debd56a60cac60639926c9b018ab5c3163d/src/components/EditorState.js#L314