i18n: add a missing space in message

The message spans over 2 lines but the C conconcatenation does not add
the needed space between the two lines.

Signed-off-by: Jean-Noel Avila <jn.avila@free.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/sequencer.c b/sequencer.c
index c54596f..b7e0a38 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2536,7 +2536,7 @@ static enum check_level get_missing_commit_check_level(void)
 		return CHECK_WARN;
 	if (!strcasecmp("error", value))
 		return CHECK_ERROR;
-	warning(_("unrecognized setting %s for option"
+	warning(_("unrecognized setting %s for option "
 		  "rebase.missingCommitsCheck. Ignoring."), value);
 	return CHECK_IGNORE;
 }