app_voicemail.c: Fix may-be-uninitialized error

A pointer to `new` is passed to `inboxcount(...)` which increments the
pointed-to value.

apps/app_voicemail.c

@@ -14176,7 +14176,7 @@ static int append_vmu_info_astman(
 		const char* actionid
 		)
 {
-	int new;
+	int new = 0;
 	int old;
 	char *mailbox;
 	int ret;