PATCH 3/6: handle the Pound token in error message

otherwise we print this:
parse error in ${...\M-D...} substitution

---

In practice, I'm not sure how to hit this path, I uncommented the
condition to test it, so maybe this is overly cautious for no gain?

 Src/subst.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Src/subst.c b/Src/subst.c
index 16a3cb055c..690d9344d9 100644
--- a/Src/subst.c
+++ b/Src/subst.c
@@ -3380,7 +3380,7 @@ paramsubst(LinkList l, LinkNode n, char **str, int qt, int pf_flags,
 		    if (haserr)
 			shtokenize(s);
 		} else if (haserr || errflag) {
-		    zerr("parse error in ${...%c...} substitution", s[-1]);
+		    zerr("parse error in ${...%c...} substitution", s[-1] == Pound ? '#' : s[-1]);
 		    return NULL;
 		}
 	    }
-- 
2.38.1