Change default dash（“-”）to blank in bootstrap table

I have a web app, frontend has a bootstrap table, backend using Restful API to render the data.

In the bootstrap table, the null value displays dash by default.

I want to change the default dash to blank for all the data.

I have tried this method:Bootstrap table, dashes / hyphens in empty cells,

    $('#bk-table').bootstrapTable({
        undefinedText: ''
    });

But it did not worked for me, the table still displays dash as default for null value, and in the console no error shows.

How could I change default dash（“-”）to blank in bootstrap table?