handle non-existent user with sync jobs

Emby.Server.Implementations/Sync/SyncJobProcessor.cs

@@ -59,15 +59,8 @@ namespace Emby.Server.Implementations.Sync
             _mediaSourceManager = mediaSourceManager;
         }
 
-        public async Task EnsureJobItems(SyncJob job)
+        public async Task EnsureJobItems(SyncJob job, User user)
         {
-            var user = _userManager.GetUserById(job.UserId);
-
-            if (user == null)
-            {
-                throw new InvalidOperationException("Cannot proceed with sync because user no longer exists.");
-            }
-
             var items = (await GetItemsForSync(job.Category, job.ParentId, job.RequestedItemIds, user, job.UnwatchedOnly).ConfigureAwait(false))
                 .ToList();
 
@@ -385,7 +378,16 @@ namespace Emby.Server.Implementations.Sync
 
                 if (job.SyncNewContent)
                 {
-                    await EnsureJobItems(job).ConfigureAwait(false);
+                    var user = _userManager.GetUserById(job.UserId);
+
+                    if (user == null)
+                    {
+                        await _syncManager.CancelJob(job.Id).ConfigureAwait(false);
+                    }
+                    else
+                    {
+                        await EnsureJobItems(job, user).ConfigureAwait(false);
+                    }
                 }
             }
         }

Emby.Server.Implementations/Sync/SyncManager.cs

@@ -181,7 +181,7 @@ namespace Emby.Server.Implementations.Sync
 
             await _repo.Create(job).ConfigureAwait(false);
 
-            await processor.EnsureJobItems(job).ConfigureAwait(false);
+            await processor.EnsureJobItems(job, user).ConfigureAwait(false);
 
             // If it already has a converting status then is must have been aborted during conversion
             var jobItemsResult = GetJobItems(new SyncJobItemQuery