omap: Move delete into if

https://github.com/hyper-carrot/goc2p/blob/master/src/basic/map1/omap.go#L58

Why not move this line into
https://github.com/hyper-carrot/goc2p/blob/master/src/basic/map1/omap.go#L59

[hyper0x]

That's good, wait for your PR.