Error: Call to a member function setAttribute() on null in views_table_rowspan_preprocess_views_view_table() (line 47 of /var/www/web/modules/contrib/views_table_rowspan/views_table_rowspan.module)

Steps to reproduce:

1. Create new name(field_name) in basic page content type.
2. Create 2 basic page node with empty name .

Node 1
Title = Page1
Body = Body2
Name =

Node 2
Title = Page2
Body = Body2
Name =

3. Create view for basic page
4. In fields add title, body , name.
5. In Format : select Table Rowspan
6. Click on Settings: check HIDE EMPTY COLUMN for name field
7. In Grouping field Nr.1 select name field.

visit the view page above error will occurs.