decoder/ffpmeg: simplify ffmpeg_send_packet()

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -332,7 +332,14 @@ ffmpeg_send_packet(Decoder &decoder, InputStream &is,
 		int len = avcodec_decode_audio4(codec_context,
 						frame, &got_frame,
 						&packet2);
-		if (len >= 0 && got_frame) {
+		if (len < 0) {
+			/* if error, we skip the frame */
+			LogDefault(ffmpeg_domain,
+				   "decoding failed, frame skipped");
+			break;
+		}
+
+		if (got_frame) {
 			audio_size = copy_interleave_frame(codec_context,
 							   frame,
 							   &output_buffer,
@@ -341,13 +348,6 @@ ffmpeg_send_packet(Decoder &decoder, InputStream &is,
 				len = audio_size;
 		}
 
-		if (len < 0) {
-			/* if error, we skip the frame */
-			LogDefault(ffmpeg_domain,
-				   "decoding failed, frame skipped");
-			break;
-		}
-
 		packet2.data += len;
 		packet2.size -= len;