w: fixing missing '-' in the FROM field when empty

With 99bebff06a058f1ebf794fca1b358d0df73fdd35 a configurable
width of the FROM column was introduced. Unfortunately this
caused a regression in the dash printing. Hopefully fixed
with this commit.

w.c

@@ -100,6 +100,10 @@ static void print_host(const char *restrict host, int len, const int fromlen)
 	 * space-fill, and a '-' too if needed to ensure the
 	 * column exists
 	 */
+	if (!width) {
+		fputc('-', stdout);
+		++width;
+	}
 	while (width++ < fromlen)
 		fputc(' ', stdout);
 }