var google.golang.org/protobuf/internal/impl.bytesZero
2 uses
google.golang.org/protobuf/internal/impl (current package)
convert.go#L86: bytesZero = protoreflect.ValueOfBytes(nil)
convert.go#L132: return &bytesConverter{t, defVal(fd, bytesZero)}
The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)