Why this change?
The `Table Builder when editing a table when cancelling table creation should close the modal if there are no changes made` system
test in `spec/system/table_builder_spec.rb` was flaky. It turns out that
when the modal is opened, we have to load some JS/CSS files. While that
is happening, the modal is actually not functional and clicking stuff
in the footer can actually result in an error. In this case, the
`interceptCloseModal` calls the private `_hasChanges` function which
then calls `this.spreadsheet.getHeaders()`. When stuff is still loading,
`this.spreadsheet` has not been set. As a result we get the following
error:
```
Cannot read properties of null (reading 'getHeaders')
```
What does this change do?
Why stuff is loading, we will now hide the footer in the modal.
7b907ec50a