Option set: Optional options attributes cause runtime errors

[thomasheartman]

As discussed on the internal slack, the minimum and maximum attributes of an option set's options element are optional (according to the schema), but XP throws a runtime exception if you try and use an option set without these specified. The error mentions a ConvertException from string to int, which can be hard to debug if you don't have any numbers in your XML.

Because the attributes are optional according to the schema, a language server or other similar service might not (mine doesn't) tell you that you need to add the attributes.

This option set demonstrates the issue.

<option-set name="set">
  <label>Os</label>
  <options>
    <option name="a">
      <label>A</label>
    </option>
  </options>
</option-set>

[rymsha]

schema should be updated to make minimum and maximum attributes required