Using the osm plugin with a simple \[[!osm]] directive does not seem to work, a "TypeError: mapProjection is null" is given. I believe this is because the client side Javascript uses the options.layers, which is always Null. 

[[!tag patch]]
I have produced a patch for this issue, but beware, while it appears to fix the problem for me, I have little understanding of perl and the existing code base.
<https://github.com/cbaines/ikiwiki/commit/4294b4c24a56c7103c48250dd9d833b42838a472>
