make sub formats preference default by default

app/src/main/java/com/deniscerri/ytdl/util/extractors/YTDLPUtil.kt

@@ -1337,7 +1337,7 @@ class YTDLPUtil(private val context: Context, private val commandTemplateDao: Co
                 }
 
                 if (downloadItem.videoPreferences.embedSubs || downloadItem.videoPreferences.writeSubs || downloadItem.videoPreferences.writeAutoSubs){
-                    val subFormat = sharedPreferences.getString("sub_format", "srt")
+                    val subFormat = sharedPreferences.getString("sub_format", "")
                     if(subFormat!!.isNotBlank()){
                         request.addOption("--sub-format", "${subFormat}/best")
                         request.addOption("--convert-subtitles", subFormat)

app/src/main/res/xml/processing_preferences.xml

@@ -202,7 +202,7 @@
 
 
         <ListPreference
-            android:defaultValue="srt"
+            android:defaultValue=""
             android:entries="@array/sub_formats"
             android:entryValues="@array/sub_formats_values"
             android:icon="@drawable/baseline_format_quote_24"