stash: add missing space to an error message

Restore a space that was lost in 8a0fc8d19d (stash: convert apply to
builtin, 2019-02-25).

Signed-off-by: Kyle Meyer <kyle@kyleam.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/stash.c

@@ -418,7 +418,7 @@ static int do_apply_stash(const char *prefix, struct stash_info *info,
 			ret = apply_cached(&out);
 			strbuf_release(&out);
 			if (ret)
-				return error(_("conflicts in index."
+				return error(_("conflicts in index. "
 					       "Try without --index."));
 
 			discard_cache();