protected free(ssl_mutexes) with ifndef NO_SSL

mongoose.c

@@ -3960,9 +3960,11 @@ static void free_context(struct mg_context *ctx) {
   if (ctx->ssl_ctx != NULL) {
     SSL_CTX_free(ctx->ssl_ctx);
   }
+#ifndef NO_SSL
   if (ssl_mutexes != NULL) {
     free(ssl_mutexes);
   }
+#endif // !NO_SSL
 
   // Deallocate context itself
   free(ctx);