fix compilation and potential runtime exception

Sources/VLCPlaybackController.m

@@ -733,7 +733,7 @@
         item = self.fileFromMediaLibrary;
     else if (self.mediaList) {
         NSArray *matches = [MLFile fileForURL:[_mediaPlayer.media.url absoluteString]];
-        item = matches.firstObject
+        item = matches.firstObject;
     }
 
     if (item) {

Sources/VLCThumbnailsCache.m

@@ -162,7 +162,8 @@
 
 - (void)_setThumbnail:(UIImage *)image forObjectId:(NSManagedObjectID *)objID
 {
-    [_thumbnailCache setObject:image forKey:objID];
+    if (image)
+        [_thumbnailCache setObject:image forKey:objID];
 }
 
 - (UIImage *)thumbnailForMediaFile:(MLFile *)mediaFile