ToolAgent has been fixed - other agents need to be checked.

If data is set to zero then it will not match any other data value.

I think some of the changes I made may partially fix this, since the Data classes were returning a SimpleData if they weren't able to parse it rather than returning null.

I did this; several weren't setting to null. I haven't verified that the change didn't break anything else though. My changes will affect anything that uses the Data classes.

I know both of us have fixed a few NPE's resulting from this change; not sure if they've all been caught, but should we close the issue?

Sounds good, we can re-open if the issue arises again.