'Text format field is required' error when saving Better Exposed filters (BEF)
I found the problem.

Navigate to the BEF settings under the view in question (like the screenshot above). 

Scroll down to  Require input before results are shown, select the checkbox, there should be a "Text on demand" field. 

Set the Text format field to one a valid text format.

Then apply the changes.

I created a video tutorial for you to follow: http://recordit.co/V75Zl4gAAl