ANDROID: fix crash passing negative duration to SOUND command

Author: chrisws

ChangeLog

@@ -1,3 +1,6 @@
+2019-14-02 (0.12.15)
+	ANDROID: fix crash passing negative duration to SOUND command
+
 2019-11-02 (0.12.15)
 	UI: ALT+F4 from edit/run now returns to edit
 	UI: avoid flicker from with ALT+F4 -e edit startup

src/platform/android/app/src/main/java/net/sourceforge/smallbasic/Sound.java

@@ -56,7 +56,7 @@ public void setSilent(boolean silent) {
    * http://stackoverflow.com/questions/2413426/playing-an-arbitrary-tone-with-android
    */
   private byte[] generateTone(int freqOfTone, int durationMillis) {
-    int numSamples = durationMillis * AUDIO_SAMPLE_RATE / 1000;
+    int numSamples = Math.max(1, durationMillis * AUDIO_SAMPLE_RATE / 1000);
     double sample[] = new double[numSamples];
     byte result[] = new byte[2 * numSamples];