Enhanced check for local audio tracks

When check is triggered code now checks that are files really exists

android/app/src/main/java/com/audiobookshelf/app/data/LocalLibraryItem.kt

@@ -18,6 +18,7 @@ import com.audiobookshelf.app.device.DeviceManager
 import com.fasterxml.jackson.annotation.JsonIgnore
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties
 import com.audiobookshelf.app.player.PLAYMETHOD_LOCAL
+import java.io.File
 import java.util.*
 
 @JsonIgnoreProperties(ignoreUnknown = true)
@@ -85,6 +86,17 @@ class LocalLibraryItem(
       episode.audioTrack?.let { at -> mutableListOf(at) }?.let { tracks -> audioTracks = tracks }
     }
     if (audioTracks.size == 0) return false
+    audioTracks.forEach {
+      // Check that metadata is not null
+      if (it.metadata === null) {
+        return false
+      }
+      // Check that file exists
+      val file = File(it.metadata!!.path)
+      if (!file.exists()) {
+        return false
+      }
+    }
     return true
   }