better_exposed_filters Undefined array key "sort_by"

Please review.

There is another problem. Because there is no default value, the data will not be updated when the data is cleared all.

MR appears to be the same as the patch so therefore not giving credit for that.

But instead of just adding an if check need to figure out why the value is missing to avoid masking a larger issue

This an issue appearing in 7.0.x ?