ensure at least one blank line will be emitted when piped.

helpers.go

@@ -69,8 +69,13 @@ func writeStdinLinesOrNothing(ch chan string) (hasStdinLines bool) {
 		go func() {
 			scanner := bufio.NewScanner(os.Stdin)
 			scanner.Buffer(make([]byte, 16*1024), 256*1024)
+			hasEmittedAtLeastOne := false
 			for scanner.Scan() {
 				ch <- strings.TrimSpace(scanner.Text())
+				hasEmittedAtLeastOne = true
+			}
+			if !hasEmittedAtLeastOne {
+				ch <- ""
 			}
 			close(ch)
 		}()