One of our production sites has all of the sudden started to throw an exception when browsing certain media folders.

As you can see it's possible to open the folder "Bo" in the tree. But when a user clicks on it they get this error message.

http://prntscr.com/lcm0sw

It's also possible to click on every image/folder beneath "Bo" in the tree without any error.

Below is the exception in the log. Seems to have something to do with a missing user?

2018-10-31 10:46:43,952 [P11208/D2/T115] ERROR Umbraco.Web.Editors.MediaController - Unhandled controller exception occurred AutoMapper.AutoMapperMappingException:

Mapping types: Media -> UserProfile Umbraco.Core.Models.Media -> Umbraco.Web.Models.ContentEditing.UserProfile

Destination path: ContentItemBasic`2.Owner.Owner

Source value: Umbraco.Core.Models.Media ---> System.NullReferenceException: Object reference not set to an instance of an object. at Umbraco.Core.Services.UserService.GetProfileById(Int32 id) at Umbraco.Web.Models.Mapping.OwnerResolver1.ResolveCore(TPersisted source) at AutoMapper.ValueResolver2.Resolve(ResolutionResult source) in c:\dev\AutoMapper\src\AutoMapper\ValueResolver.cs:line 12 at System.Linq.Enumerable.Aggregate[TSource,TAccumulate](IEnumerable1 source, TAccumulate seed, Func3 func) at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.MapPropertyValue(ResolutionContext context, IMappingEngineRunner mapper, Object mappedObject, PropertyMap propertyMap) in c:\dev\AutoMapper\src\AutoMapper\Mappers\TypeMapObjectMapperRegistry.cs:line 116 --- End of inner exception stack trace --- at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.MapPropertyValue(ResolutionContext context, IMappingEngineRunner mapper, Object mappedObject, PropertyMap propertyMap) in c:\dev\AutoMapper\src\AutoMapper\Mappers\TypeMapObjectMapperRegistry.cs:line 153 at AutoMapper.Mappers.TypeMapObjectMapperRegistry.PropertyMapMappingStrategy.Map(ResolutionContext context, IMappingEngineRunner mapper) in c:\dev\AutoMapper\src\AutoMapper\Mappers\TypeMapObjectMapperRegistry.cs:line 89 at AutoMapper.Mappers.TypeMapMapper.Map(ResolutionContext context, IMappingEngineRunner mapper) in c:\dev\AutoMapper\src\AutoMapper\Mappers\TypeMapMapper.cs:line 22 at AutoMapper.MappingEngine.AutoMapper.IMappingEngineRunner.Map(ResolutionContext context) in c:\dev\AutoMapper\src\AutoMapper\MappingEngine.cs:line 250 at AutoMapper.MappingEngine.Map[TSource,TDestination](TSource source) in c:\dev\AutoMapper\src\AutoMapper\MappingEngine.cs:line 78 at System.Linq.Enumerable.WhereSelectArrayIterator2.MoveNext() at System.Collections.Generic.List1..ctor(IEnumerable1 collection) at System.Linq.Enumerable.ToList[TSource](IEnumerable1 source) at Umbraco.Web.WebApi.Filters.FilterAllowedOutgoingMediaAttribute.OnActionExecuted(HttpActionExecutedContext actionExecutedContext) at System.Web.Http.Filters.ActionFilterAttribute.OnActionExecutedAsync(HttpActionExecutedContext actionExecutedContext, CancellationToken cancellationToken)