omitempty incorrectly looks at values behind pointers

[joukewitteveen]

isEmpty is called on a fully dereferenced struct, but if the original field type of the struct was a pointer to a struct, then omitempty should be taken to mean "drop if nil, otherwise output". In other words: isEmpty on any pointer type should return true precisely when the pointer is nil. This is currently not what happens because the field value is fully dereferenced.

This is a leftover from #360. The issue is demonstrated by the failure in #370.

[arp242]

I can confirm it broke in the v1.2.0 release; it works as expected in v1.1.0. It's probably d138d7a that introduced this; that changed it to always call eindirect.

Not sure yet when I'll look at this, but happy to review and accept patches in the meanwhile.