In a certain column, I am trying to replace any cell with a null value with a single space. I am trying to combine multiple rows where each row only contains one letter. When I join multi-valued cells, Refine will (understandably) throw out the null values, resulting in a large string of text with no spaces between words.
I have found several articles describing how to delete rows with null cells, but not add a space to null cells.
fwiw, below is the article I followed to join multi-valued cells http://onlinejournalismblog.com/2014/05/30/how-to-combine-multiple-rows-in-a-dataset-where-text-is-split-across-them-open-refine/#more-18955
When you use join multi-valued cells Refine ask you what separator you wish to use. The default is , (comma space). You can edit this to be a single space.
Alternatively did you try to create a text facet and bulk edit the (blank) value with a single space before using join multi-valued cells?