Fail on empty AudioRecord read()

If read() returns 0, then there is no data. According to the
documentation, it happens if the buffer is not a direct buffer:
<https://developer.android.com/reference/android/media/AudioRecord#read(java.nio.ByteBuffer,%20int)>

Refs #3812 <#3812>

server/src/main/java/com/genymobile/scrcpy/AudioCapture.java

@@ -111,7 +111,7 @@ public void stop() {
     @TargetApi(Build.VERSION_CODES.N)
     public int read(ByteBuffer directBuffer, int size, MediaCodec.BufferInfo outBufferInfo) {
         int r = recorder.read(directBuffer, size);
-        if (r < 0) {
+        if (r <= 0) {
             return r;
         }
 

server/src/main/java/com/genymobile/scrcpy/AudioEncoder.java

@@ -92,7 +92,7 @@ private void inputThread(MediaCodec mediaCodec, AudioCapture capture) throws IOE
             InputTask task = inputTasks.take();
             ByteBuffer buffer = mediaCodec.getInputBuffer(task.index);
             int r = capture.read(buffer, READ_SIZE, bufferInfo);
-            if (r < 0) {
+            if (r <= 0) {
                 throw new IOException("Could not read audio: " + r);
             }