Check for nullable last activity list sync

(cherry picked from commit 4a740acb801a04bc2ead45d272d493f4ec46f7e8)

src/NzbDrone.Core/ImportLists/FetchAndParseImportListService.cs

@@ -49,7 +49,7 @@ namespace NzbDrone.Core.ImportLists
                 var importListLocal = importList;
                 var importListStatus = _importListStatusService.GetLastSyncListInfo(importListLocal.Definition.Id);
 
-                if (DateTime.UtcNow < (importListStatus + importListLocal.MinRefreshInterval))
+                if (importListStatus.HasValue && DateTime.UtcNow < importListStatus + importListLocal.MinRefreshInterval)
                 {
                     _logger.Trace("Skipping refresh of Import List {0} due to minimum refresh inverval", importListLocal.Definition.Name);
                     continue;
@@ -102,7 +102,7 @@ namespace NzbDrone.Core.ImportLists
 
             var importListStatus = _importListStatusService.GetLastSyncListInfo(importList.Definition.Id);
 
-            if (DateTime.UtcNow < (importListStatus + importList.MinRefreshInterval))
+            if (importListStatus.HasValue && DateTime.UtcNow < importListStatus + importList.MinRefreshInterval)
             {
                 _logger.Trace("Skipping refresh of Import List {0} due to minimum refresh inverval", importList.Definition.Name);
                 return result;

src/NzbDrone.Core/ImportLists/ImportListStatus.cs

@@ -5,6 +5,6 @@ namespace NzbDrone.Core.ImportLists
 {
     public class ImportListStatus : ProviderStatusBase
     {
-        public DateTime LastInfoSync { get; set; }
+        public DateTime? LastInfoSync { get; set; }
     }
 }

src/NzbDrone.Core/ImportLists/ImportListStatusService.cs

@@ -8,7 +8,7 @@ namespace NzbDrone.Core.ImportLists
 {
     public interface IImportListStatusService : IProviderStatusServiceBase<ImportListStatus>
     {
-        DateTime GetLastSyncListInfo(int importListId);
+        DateTime? GetLastSyncListInfo(int importListId);
 
         void UpdateListSyncStatus(int importListId);
     }
@@ -20,7 +20,7 @@ namespace NzbDrone.Core.ImportLists
         {
         }
 
-        public DateTime GetLastSyncListInfo(int importListId)
+        public DateTime? GetLastSyncListInfo(int importListId)
         {
             return GetProviderStatus(importListId).LastInfoSync;
         }