Unit test for Data Provider dialog in Calc

[Regina Henschel]

Hi all,

I propose the fix https://gerrit.libreoffice.org/c/core/+/192929
Problem is, that a unit test requires Python. I do not know Python and I 
cannot test it on Windows. Does someone would like to add a unit test to 
my fix?

Or should I submit it without unit test?

Kind regards,
Regina