[fix] Fix the default source shown is spreadsheet

The RPM was shown by default in the spreadsheet. The measurement grid was created before but setted the active source to None. We need to do the same thing for the RPM so it's not displayed in the spreadsheet.

If we let the RPM shown in spreadsheet view, it force the default Attribute to "row data" for other futur empty source. So when we create a stream (which does not have any data for now), the attribute is set to "row data". When data arrived, the stream fill the attribute "Point Data", and let empty "raw data". The user will think that the spreadsheet is not working because he won't be able to see the data.