NaN value in data tip causes error

I am using dataTipTextRow to create custom data tips for my plot. I have found that when there is a NaN value in the Value field, I get an error when I click on the associated marker in the plot. Instead of my custom data tip I get the following text in a box:

Error unable to convert 'string' value to 'char'

The other points in the same plot object are able to display their data tips properly. I haven't figured out a way to determine exactly which line of code this error is happening on. Any ideas on how to fix this?