Allowing blank/null for numeric setting - only works online?

Hi All,

Bit of an odd one. I have some numeric setting fields which default to blank to imply automatic handling (e.g., if the user does not specify a y-axis upper limit, then it is automatically determined from the data):

With corresponding `capabilities.json` entry:

When working with the visual in the PowerBI service, it has no issues allowing users to add and remove values.

But when working in PowerBI Desktop, if a user adds a value and then tries to remove it, then an error is displayed until a number is entered:

But it can be dismissed by resetting all settings to defaults:

Is this something that should be working/allowed?

Alternatively, is there a recommended way to handle optional/blank/null numeric values?

Thanks!
Andrew