500 error in thumbnail controller

Description

1. Add VectorImageFile.cs to Models > Media.

[ContentType(GUID = "F522B459-EB27-462C-B216-989FC7FF9448")]
[MediaDescriptor(ExtensionString = "svg")]
public class VectorImageFile : ImageData
{
    /// <summary>
    /// Gets the generated thumbnail for this media.
    /// </summary>
    public override Blob Thumbnail
    {
        get { return BinaryData; }
    }
}

2. Upload an svg file.
3. Add an svg file to the Alloy Plans teaser image property.

Expected:
No 500 error

Actual:
500 error

2019-03-28 17:04:17,520 [212] ERROR EPiServer.Global: Unhandled exception in ASP.NET
System.ArgumentNullException: Value cannot be null.
Parameter name: value
   at System.Web.Caching.CacheEntry..ctor(String key, Object value, CacheDependency dependency, CacheItemRemovedCallback onRemovedHandler, DateTime utcAbsoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, Boolean isPublic, CacheInternal cache)
   at System.Web.Caching.CacheInternal.DoInsert(Boolean isPublic, String key, Object value, CacheDependency dependencies, DateTime utcAbsoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, Boolean replace)
   at System.Web.Caching.AspNetCache.Add(String key, Object item, CacheInsertOptions options)
   at System.Web.Caching.Cache.Add(String key, Object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback)
   at EPiServer.Cms.Shell.UI.Controllers.Internal.ThumbnailController.Generate(ContentReference contentLink)
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass24_0.<InvokeActionMethodWithFilters>b__0()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)
   at System.Web.Mvc.Controller.ExecuteCore()
   at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
   at EPiServer.Shell.Web.Mvc.ModuleMvcHandler.ProcessController(IController controller)
   at EPiServer.Shell.Web.Mvc.ModuleMvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.<>c__DisplayClass285_0.<ExecuteStepImpl>b__0()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
System.ArgumentNullException: Value cannot be null.
Parameter name: value
   at System.Web.Caching.CacheEntry..ctor(String key, Object value, CacheDependency dependency, CacheItemRemovedCallback onRemovedHandler, DateTime utcAbsoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, Boolean isPublic, CacheInternal cache)
   at System.Web.Caching.CacheInternal.DoInsert(Boolean isPublic, String key, Object value, CacheDependency dependencies, DateTime utcAbsoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback, Boolean replace)
   at System.Web.Caching.AspNetCache.Add(String key, Object item, CacheInsertOptions options)
   at System.Web.Caching.Cache.Add(String key, Object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback)
   at EPiServer.Cms.Shell.UI.Controllers.Internal.ThumbnailController.Generate(ContentReference contentLink)
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass24_0.<InvokeActionMethodWithFilters>b__0()
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation)
   at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)
   at System.Web.Mvc.Controller.ExecuteCore()
   at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
   at EPiServer.Shell.Web.Mvc.ModuleMvcHandler.ProcessController(IController controller)
   at EPiServer.Shell.Web.Mvc.ModuleMvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.<>c__DisplayClass285_0.<ExecuteStepImpl>b__0()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)