Fixed: Loading queue with pending releases for deleted artists

(cherry picked from commit 38c0135d7cd05b22bede934f8571c439dcf70a88)

Closes #5214

src/NzbDrone.Core/Datastore/Extensions/BuilderExtensions.cs

@@ -64,19 +64,25 @@ namespace NzbDrone.Core.Datastore
         public static SqlBuilder Join<TLeft, TRight>(this SqlBuilder builder, Expression<Func<TLeft, TRight, bool>> filter)
         {
             var wb = GetWhereBuilder(builder.DatabaseType, filter, false, builder.Sequence);
-
             var rightTable = TableMapping.Mapper.TableNameMapping(typeof(TRight));
 
-            return builder.Join($"\"{rightTable}\" ON {wb.ToString()}");
+            return builder.Join($"\"{rightTable}\" ON {wb}");
         }
 
         public static SqlBuilder LeftJoin<TLeft, TRight>(this SqlBuilder builder, Expression<Func<TLeft, TRight, bool>> filter)
         {
             var wb = GetWhereBuilder(builder.DatabaseType, filter, false, builder.Sequence);
+            var rightTable = TableMapping.Mapper.TableNameMapping(typeof(TRight));
+
+            return builder.LeftJoin($"\"{rightTable}\" ON {wb}");
+        }
 
+        public static SqlBuilder InnerJoin<TLeft, TRight>(this SqlBuilder builder, Expression<Func<TLeft, TRight, bool>> filter)
+        {
+            var wb = GetWhereBuilder(builder.DatabaseType, filter, false, builder.Sequence);
             var rightTable = TableMapping.Mapper.TableNameMapping(typeof(TRight));
 
-            return builder.LeftJoin($"\"{rightTable}\" ON {wb.ToString()}");
+            return builder.InnerJoin($"\"{rightTable}\" ON {wb}");
         }
 
         public static SqlBuilder GroupBy<TModel>(this SqlBuilder builder, Expression<Func<TModel, object>> property)

src/NzbDrone.Core/Download/Pending/PendingReleaseRepository.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using NzbDrone.Core.Datastore;
 using NzbDrone.Core.Messaging.Events;
+using NzbDrone.Core.Music;
 
 namespace NzbDrone.Core.Download.Pending
 {
@@ -30,7 +31,11 @@ namespace NzbDrone.Core.Download.Pending
 
         public List<PendingRelease> WithoutFallback()
         {
-            return Query(p => p.Reason != PendingReleaseReason.Fallback);
+            var builder = new SqlBuilder(_database.DatabaseType)
+                .InnerJoin<PendingRelease, Artist>((p, s) => p.ArtistId == s.Id)
+                .Where<PendingRelease>(p => p.Reason != PendingReleaseReason.Fallback);
+
+            return Query(builder);
         }
     }
 }

src/NzbDrone.Core/Download/Pending/PendingReleaseService.cs

@@ -273,10 +273,7 @@ namespace NzbDrone.Core.Download.Pending
             {
                 foreach (var artist in knownRemoteAlbums.Values.Select(v => v.Artist))
                 {
-                    if (!artistMap.ContainsKey(artist.Id))
-                    {
-                        artistMap[artist.Id] = artist;
-                    }
+                    artistMap.TryAdd(artist.Id, artist);
                 }
             }
 
@@ -292,7 +289,7 @@ namespace NzbDrone.Core.Download.Pending
                 // Just in case the artist was removed, but wasn't cleaned up yet (housekeeper will clean it up)
                 if (artist == null)
                 {
-                    return null;
+                    continue;
                 }
 
                 release.RemoteAlbum = new RemoteAlbum