Address panic on closing a previously closed channel (#1613)
Address panic on closing a previously closed channel (#1613)

+ Fixes: https://github.com/blevesearch/bleve/issues/1609

panic: close of closed channel

goroutine 68 [running]:
github.com/blevesearch/bleve/v2/index/scorch.(*closeChWrapper).close(0xc000346b80)
	/Users/runner/work/bleve/bleve/index/scorch/merge.go:228 +0x99
github.com/blevesearch/bleve/v2/index/scorch.(*closeChWrapper).listen(0xc000346b80)
	/Users/runner/work/bleve/bleve/index/scorch/merge.go:235 +0x1cd
created by github.com/blevesearch/bleve/v2/index/scorch.(*Scorch).planMergeAtSnapshot
	/Users/runner/work/bleve/bleve/index/scorch/merge.go:275 +0x4ba
blevesearch/bleve,blevesearch/bleve