Fixed: Don't set missing release dates to 0001-01-01

src/NzbDrone.Core/MetadataSource/SkyHook/Resource/AlbumResource.cs

@@ -15,7 +15,7 @@ namespace NzbDrone.Core.MetadataSource.SkyHook.Resource
         public List<ImageResource> Images { get; set; }
         public List<LinkResource> Links { get; set; }
         public RatingResource Rating { get; set; }
-        public DateTime ReleaseDate { get; set; }
+        public DateTime? ReleaseDate { get; set; }
         public List<ReleaseResource> Releases { get; set; }
         public List<string> SecondaryTypes { get; set; }
         public string Title { get; set; }

src/NzbDrone.Core/MetadataSource/SkyHook/Resource/ReleaseResource.cs

@@ -7,7 +7,7 @@ namespace NzbDrone.Core.MetadataSource.SkyHook.Resource
     {
         public string Disambiguation { get; set; }
         public List<string> Country { get; set; }
-        public DateTime ReleaseDate { get; set; }
+        public DateTime? ReleaseDate { get; set; }
         public string Id { get; set; }
         public List<string> Label { get; set; }
         public List<MediumResource> Media { get; set; }