Retrieving number facets does not handle incorrectly config'd facet fields

[ci-richard-mcelhinney]

There is potential for standard facets on Control Points to be configured with a different type than expected. For example, the Niagara documentation states that the Min facet field should be a Number. However, the user can configure this to be something else.

This causes a Class Cast Exception when trying to retrieve the facet as the type is unexpected.

Need to add some better handling for this so it doesn't crash out.