Filter.js Does Not Filter Instances where a single value exists instead of an array value

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Selecting "Carder" returns 0 results where it should return 4. The issue is the filter works for people with either null values or multiple values for "Occupation" or "Location" but does NOT work when the individual only has a single value for the filter in question. An example record is "John Hern (b. 1800)".
Related categories: PHP JavaScript AJAX HTML jQuery / Prototype