Ignore blanks when calculating %

Hello All,

I have researched this for hours but have been unable to resolve it.  Any help would be appreciated.

I have survey data.  Of course, sometimes respondents do not answer every question. 

Here is an example of my data:

I have a bar graph displaying the % of respondents who answered with each response.  It is sorted in order (Strongly Agree, Agree, Disagree, Strongly Disagree)

Here is my dax:

% = DIVIDE([RespondentIDUniqueCount],CALCULATE([RespondentIDUniqueCount],ALL('Survey'[The class was very helpful],'Survey'[The class was very helpful Order Sort])))

 

The problem is that I don't want those who didn't answer the question to be included in the calculation or the bar graph, for example, like this where it shows (Blank):

 

 

I do not want to simply filter out the blanks in the visual because then the total percentages do not equal 100%, of course. 

I should also add that I do not want to remove the entire row, as the person may have answered other questions on the survey but left that particular question blank.

 

Thank you for any help you can offer!