ensures the generic base class static query instance is lazily created

src/Umbraco.Core/Persistence/Mappers/MappingResolver.cs

@@ -43,7 +43,7 @@ namespace Umbraco.Core.Persistence.Mappers
                     {
                         return byAttribute.Result;
                     }
-                    throw new Exception("Invalid Type: A Mapper could not be resolved based on the passed in Type");
+                    throw new Exception("Invalid Type: A Mapper could not be resolved based on the passed in Type " + type);
                 });
         }
 

src/Umbraco.Core/Persistence/Repositories/RepositoryBase.cs

@@ -85,7 +85,7 @@ namespace Umbraco.Core.Persistence.Repositories
 
         #region Static Queries
 
-        private readonly IQuery<TEntity> _hasIdQuery = Query<TEntity>.Builder.Where(x => x.Id != 0);
+        private IQuery<TEntity> _hasIdQuery;
 
         #endregion
 
@@ -117,6 +117,12 @@ namespace Umbraco.Core.Persistence.Repositories
                     RuntimeCache,
                     new RepositoryCachePolicyOptions(() =>
                     {
+                        //create it once if it is needed (no need for locking here)
+                        if (_hasIdQuery == null)
+                        {
+                            _hasIdQuery = Query<TEntity>.Builder.Where(x => x.Id != 0);
+                        }
+
                         //Get count of all entities of current type (TEntity) to ensure cached result is correct
                         return PerformCount(_hasIdQuery);
                     })));