Bug: Extra row in Frequency Distribution results

This is a bug in Prism 6.00, 6.01, 6.0a, and 6.0b. 

Say that you set the center of the first bin to 5, the center of the last bin to be 15, and the bin width to 10. Tthe first bin includes values from 0 to just a tiny bit below 10. The second bin includes values from 10 to just a tiny bit below 20. If there is a value of exactly 20, Prism will place it into a third bin, that is not labeled. So there is an extra row in the results, a row with a Y value (a count or frequency) but no row label to identify what that row is for.

We'll fix the next release of Prism so 20 would simply not fit either bin in the example above, so the results would stop with two labeled rows.