options array isn't checked to verify that it's an array

I just ran into an issue where I wasn't passing in an array to variable_get_value(), I was passing in a default value (like variable_get()), and the variable module was throwing errors and white screening. It took me awhile to figure out my issue, but once I did it worked great. After looking at your code I realized that if you were to add an array check like this:

function _variable_options(array $options = array()) {

That would throw an error sooner, and be much easier to find the problem for any future developers.