patch 9.0.1863: wrong format specifiers in e_aptypes_is_null_str_nr

Problem:  wrong format specifiers in e_aptypes_is_null_str_nr
Solution: Fix the wrong format specifier

closes: #13020

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/strings.c b/src/strings.c
index cb044ec..710b1d3 100644
--- a/src/strings.c
+++ b/src/strings.c
@@ -2801,7 +2801,7 @@
 
 	if (ap_types == NULL || ap_types[*arg_cur] == NULL)
 	{
-	    semsg(e_aptypes_is_null_str_nr, fmt, *arg_cur);
+	    siemsg(e_aptypes_is_null_str_nr, fmt, *arg_cur);
 	    return;
 	}