The culprit seems to be that baseview's WindowInner::close is called twice.
Standalone, VST3 and CLAP work as expected, but closing the standalone version seems to still lead to a null pointer dereference. Causes this error message to pop up after closing.
With these changes, building the nih_plug_gain_iced example fails at compile time.
Okay so, actually, depending on the macos_fix branch of baseview in both this crate and nih-plug made a window successfully open! The editor still crashes currently, but that's just because of a...
Yeah, this does seem to just be a baseview issue, I should probably report it there and not here?
Not an expert on cocoa / macOS APIs in general but I'd be down to help fix this in any way possible.