DMP-4385 Filter out 0 second audios from ATS processing

Added tests for ATS filtering to filter out audio files that have less than a second apart

src/main/java/uk/gov/hmcts/darts/audio/component/impl/OutboundFileProcessorImpl.java

@@ -103,7 +103,7 @@ public List<AudioFileInfo> processAudioForPlaybacks(Map<MediaEntity, Path> media
             // Used for logging only
             String audioFilenames = null;
             if (log.isDebugEnabled()) {
-                audioFileInfos.stream().map(AudioFileInfo::getMediaFile).collect(Collectors.joining(", "));
+                audioFilenames = audioFileInfos.stream().map(AudioFileInfo::getMediaFile).collect(Collectors.joining(", "));
             }
 
             List<ChannelAudio> concatenationsList = new ArrayList<>();