siputils: fix for e164_check()

- the condition for non-digit matching was always false

(cherry picked from commit 160710af0ab85dbf211fa7d445d6d4be9b66db10)

modules/siputils/checks.c

@@ -423,7 +423,7 @@ static inline int e164_check(str* _user)
 	char c;
 
 	if ((_user->len > 2) && (_user->len < 17) && ((_user->s)[0] == '+')) {
-		for (i = 1; i <= _user->len; i++) {
+		for (i = 1; i < _user->len; i++) {
 			c = (_user->s)[i];
 			if (c < '0' || c > '9') return -1;
 		}