math extension: issue with undefined targets

[pkra]

We ran into what looks like a bug in the math extension. I couldn't quite identify the corresponding part in the XML but it seems the issue is the following.

In https://github.com/elifesciences/lens/blob/master/extensions/math/math_converter.js#L671-L676, should referencedMath[targetNode.id] = true; be inside the preceding if (targetNode) { ... }?

[pkra]

To add some background. This was caused by a JATS file with appendices and references into theorem environments in the appendices. Lens drops the appendices (I think that's intentional, correct?) and thus there is no target for the reference.