How to create a legend for a row in a parts-of-whole table that is zero?

Prism 6 can create parts-of-whole graphs like pie charts, and can include legends for each "slice". However, if one of the rows of data is zero, then Prism will not create a legend for it.

In some cases, you may want a legend, even though the value is zero. This might make sense when you are creating a series of similar graphs, and the value is not zero in other graphs. Here is a trick to do that. Instead of zero, enter some tiny nonzero value like 0.000001. The slice will be invisible on the graph, but Prism will create a legend for it.