Even when something is a user error it should ideally not lead to a crash, with the exceptions of nodes/shaders which the baker doesn't have any control over. Baking onto self should work, it was a feature added some version(s) ago.
In this case it's a double whammy.
1) A bug for a circumstance I missed. When baking onto self and the mesh contains non-UV mapped polys mixed with mapped polys. If you hide the non-UV polys the current version will be able to deal with it, until I fixed it and put up a new version.
2) The Amb Occlusion node will also crash, if multithreading is enabled in the baker (i.e. set to something other than 1 Thread). At least it does with the DP Kit version I still have, which admittedly is quite old, so maybe that issue has been fixed.
Note that unfortunately even if the Amb Occlusion doesn't crash, you won't actually get any AO applied from it, because that node relies on Layout functionality to produce results. If you want AO you could let the baker generate an "Occlusion/Dirt Map" instead.