check nb_samples

app/src/main/cpp/visualizer/execute_fft.cpp

@@ -228,7 +228,10 @@ void release_visualizer(filter_sys_t *p_filter)
 }
 
 int ensure_memory(filter_sys_t *fft_filter, int nb_samples) {
-    if (nb_samples != fft_filter->nb_samples && nb_samples >= MIN_FFT_SIZE) {
+    if (nb_samples < MIN_FFT_SIZE) {
+        return -1;
+    }
+    if (nb_samples != fft_filter->nb_samples) {
         if (!fft_filter->data) {
             fft_filter->data_size = nb_samples;
             fft_filter->data = (uint8_t *) (malloc(nb_samples * sizeof(uint8_t)));