"Jump to Report" hyperlink only if there is data?

I basically want to disable the "Jump to Report" ability in my report if the column has a sum of 0. If the sum is greater than 0 I want it to allow hyperlinking.

Here is what I have in the textbox "Jump to Report" section (where you select the sub report from the dropdown)

=Iif(Fields!Not_Patched.Value > 0, "subRPT_Enterprise Vulnerability Report By PLUS", False)

This works, however I get the following Warning when running the report...

[rsInvalidExpressionDataType] The DrillthroughReportName expression used in chart ‘chart1.DataPoint.ActionInfo.Action’ returned a data type that is not valid.
Preview complete -- 0 errors, 1 warnings

Can anyone assist in why I'm getting this warning? I have tried to search this forum and google but no answers...

Instead of False use Nothing:

=Iif(Fields!Not_Patched.Value > 0, "subRPT_Enterprise Vulnerability Report By PLUS", Nothing)

Thanks, Donovan.