The first noticeable thing whenever the style dialog is opened is some empty space at its top.
Solved it using a function intrinsic to Inkscape’s Panel class. Just packing the _mainbox that contains all the elements of style dialog to get_contents, the unwanted space issue was solved. Well it took quite a time to figure it out!
Coming next to recent implementation of deleting a selector, it worked well except in the case when the last and only remaining selector was deleted. This was because _sValue was empty and using the following statement:
actually had NULL as argument to append() function. So after clearing the _sValue, content was only appended to it if some selectors were still present in the document.