missing variables

if a user has a broken variable, like a query that doesn't return anything, they currently can't use that variable with flux auto completion, because it doesn't generate a proper AST

feels like we should allow a variable to be broken, let the user finish their copy pasta job, and then have the dashboard start working once they fix their variable.

The issue concerns Flux auto-completion and AST generation; start by locating the auto-completion entry point and the code that builds the AST for variables. Reproduce a variable whose query returns nothing, then verify that completion remains available and the dashboard works after the variable is fixed.

Written by the indexing model from the issue text.