Add defensive checks to our missing asset to ensure we only add it if our track matches the media type

Author: vade

Sources/OpenTimelineIO-AVFoundation/OpenTimelineIO-Extensions/Clip.swift

@@ -13,23 +13,29 @@ import TimecodeKit
 extension Clip
 {
     // see https://opentimelineio.readthedocs.io/en/latest/tutorials/time-ranges.html
-    func toAVAssetAndMapping(baseURL:URL? = nil, useTimecode:Bool = true, rescaleToAsset:Bool = true) throws -> (asset:AVAsset, timeMaping:CMTimeMapping)?
+    func toAVAssetAndMapping(baseURL:URL? = nil, trackType:AVMediaType,  useTimecode:Bool = true, rescaleToAsset:Bool = true) throws -> (asset:AVAsset, timeMaping:CMTimeMapping)?
     {
 
         let asset:AVURLAsset
 
         if let externalReference = self.mediaReference as? ExternalReference,
             let maybeAsset = externalReference.toAVAsset(baseURL: baseURL)
         {
+            
+            guard !maybeAsset.tracks(withMediaType: trackType).isEmpty else { return nil }
+            
             asset = maybeAsset
         }
         else
         {
             //see AWS Picchu Edit - Premiere cant import either?
             //we have a generator or just a dead reference?
             let missingMediaURL = Bundle.main.url(forResource: "MediaNotFound", withExtension: "mp4")!
+            let missingAsset = AVURLAsset(url: missingMediaURL)
+            
+            guard !missingAsset.tracks(withMediaType: trackType).isEmpty else { return nil }
 
-            asset = AVURLAsset(url: missingMediaURL)
+            asset = missingAsset
         }
 
         var timeRangeInAsset = try self.trimmedRange()

Sources/OpenTimelineIO-AVFoundation/OpenTimelineIO-Extensions/Timeline.swift

@@ -78,7 +78,7 @@ public extension Timeline
             {
                 guard
                     let clip = item as? Clip,
-                    let (sourceAsset, clipTimeMapping) = try clip.toAVAssetAndMapping(baseURL: baseURL, useTimecode: useAssetTimecode, rescaleToAsset: rescaleToAsset),
+                    let (sourceAsset, clipTimeMapping) = try clip.toAVAssetAndMapping(baseURL: baseURL, trackType:.video, useTimecode: useAssetTimecode, rescaleToAsset: rescaleToAsset),
                     let sourceAssetFirstVideoTrack = try await sourceAsset.loadTracks(withMediaType: .video).first,
                     let compositionVideoTrack = compositionVideoTrack //composition.mutableTrack(compatibleWith: sourceAssetFirstVideoTrack) ??
                 else