Post Date filter bug

There is a bug in how the post_date filter works.

On line 432, you have the following:

$post_date = explode("+", esc_attr(urlencode($wp_query->query['post_date'])));

This works fine if you have two dates, which are concatenated with a + symbol.

However, if you only use a single datepicker, the + is not present, and this means $post_date is never populated, as the + is not added in.