Consider adding the ability to warn and return null for fields that are missing

[rbalicki2]

• it might be nice to be able to select non-existent fields, and have them return null, instead of failing to compile (in dev mode), because the workflow of "create parent component -> select non-existent child component -> refresh page to see parent component sorta working -> write the child component" is nice
• alternatively, maybe an annotation on a selection "@todo" that errors in prod mode but not in dev mode
• this might be less of a need once we have the language server, because you will be able to select the child component and use an autofix to create the child component. NICE