Fix the double free and NULL derefs in the custom io cleanup paths

Author: aidangarske

custom-io-callbacks/file-server/file-server.c

@@ -186,7 +186,7 @@ int main(int argc, char** argv)
 //    sslServ = Server(&ctxServ, "ECDHE-RSA-AES128-SHA", 1);
     sslServ = Server(&ctxServ, "let-wolfssl-choose", 0);
 
-    if (sslServ == NULL) { printf("sslServ NULL\n"); return -1;}
+    if (sslServ == NULL) { printf("sslServ NULL\n"); goto cleanup; }
     ret = SSL_FAILURE;
     printf("Starting server\n");
     while (ret != SSL_SUCCESS) {