Error in my iOS app

gistfile1.m

//
// app delegate
//

RKObjectManager *manager = [RKObjectManager objectManagerWithBaseURL:@"http://129.21.140.120:8080"];
    manager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:@"db.sqlite"];
    //manager.objectStore.managedObjectCache = [[CustomCache alloc] init];
    manager.client.requestQueue.showsNetworkActivityIndicatorWhenBusy = YES;
    manager.acceptMIMEType = RKMIMETypeJSON; 
    manager.serializationMIMEType = RKMIMETypeJSON;
    
    manager.client.authenticationType = RKRequestAuthenticationTypeHTTP;
    manager.client.username = username;
    manager.client.password = password;
    
    RKObjectRouter *router = [[RKObjectRouter alloc] init];
    [router routeClass:[List class] toResourcePath:@"/lists/:listID"];
    [router routeClass:[List class] toResourcePath:@"/lists" forMethod:RKRequestMethodPOST];
    [router routeClass:[Task class] toResourcePath:@"/lists/:list.listID/tasks/:taskID"];
    [router routeClass:[Task class] toResourcePath:@"/lists/:list.listID/tasks/" forMethod:RKRequestMethodPOST];
    manager.router = router;
    
    
    RKManagedObjectMapping *taskMapping = [RKManagedObjectMapping mappingForClass:[Task class]];
    taskMapping.primaryKeyAttribute = @"taskID";
    [taskMapping mapKeyPath:@"id" toAttribute:@"taskID"];
    [taskMapping mapAttributes:@"title", @"body", @"priority", nil];
    [manager.mappingProvider setMapping:taskMapping forKeyPath:@"task"];
    [manager.mappingProvider setSerializationMapping:[taskMapping inverseMapping] forClass:[Task class]];
    
    RKManagedObjectMapping *listMapping = [RKManagedObjectMapping mappingForClass:[List class]];
    listMapping.primaryKeyAttribute = @"listID";
    [listMapping mapAttributes:@"title", nil];
    [listMapping mapKeyPath:@"id" toAttribute:@"listID"];
    [listMapping mapRelationship:@"tasks" withMapping:taskMapping];
    [manager.mappingProvider setMapping:listMapping forKeyPath:@"list"];
    [manager.mappingProvider setSerializationMapping:[listMapping inverseMapping] forClass:[List class]];
    
    NSLog(@"App Delegate 64: Manager: %@", manager);

//
//To load objects...
//

[[RKObjectManager sharedManager] loadObjectsAtResourcePath:@"/lists" delegate:self block:^(RKObjectLoader* loader) {
        // Returns lists as a naked array in JSON, so we instruct the loader
        // to user the appropriate object mapping
        loader.objectMapping = [[RKObjectManager sharedManager].mappingProvider objectMappingForClass:[List class]];
    }];



//
// Error!!
//

2012-01-31 13:24:31.557 RestkitDebugger[80474:15007] D restkit.network:RKObjectLoader.m:213 No object mapping provider, using mapping provider from parent object manager to perform KVC mapping
2012-01-31 13:24:31.559 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:255 Performing object mapping sourceObject: (
        {
        "created_at" = "2012-01-29T03:56:25Z";
        id = 31;
        "syncing_id" = 6;
        tasks =         (
                        {
                body = "";
                completed = 0;
                "created_at" = "2012-01-30T21:55:16Z";
                "creation_source" = "";
                "due_date" = "2012-01-30T21:55:00Z";
                id = 10;
                "list_id" = 31;
                priority = 1;
                "syncing_id" = "<null>";
                "time_estimate" = "<null>";
                title = Derp;
                "updated_at" = "2012-01-30T21:55:16Z";
            }
        );
        title = Test;
        "updated_at" = "2012-01-29T03:56:25Z";
        "user_id" = 1;
    }
)
 and targetObject: (null)
2012-01-31 13:24:31.560 RestkitDebugger[80474:15007] T restkit.object_mapping:RKObjectMapper.m:269 Examining keyPath 'list' for mappable content...
2012-01-31 13:24:31.560 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:104 Found a collection containing only NSNull values, considering the collection unmappable...
2012-01-31 13:24:31.561 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:279 Found unmappable value at keyPath: list
2012-01-31 13:24:31.562 RestkitDebugger[80474:15007] T restkit.object_mapping:RKObjectMapper.m:269 Examining keyPath 'error' for mappable content...
2012-01-31 13:24:31.563 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:104 Found a collection containing only NSNull values, considering the collection unmappable...
2012-01-31 13:24:31.564 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:279 Found unmappable value at keyPath: error
2012-01-31 13:24:31.565 RestkitDebugger[80474:15007] T restkit.object_mapping:RKObjectMapper.m:269 Examining keyPath 'errors' for mappable content...
2012-01-31 13:24:31.565 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:104 Found a collection containing only NSNull values, considering the collection unmappable...
2012-01-31 13:24:31.568 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:279 Found unmappable value at keyPath: errors
2012-01-31 13:24:31.569 RestkitDebugger[80474:15007] T restkit.object_mapping:RKObjectMapper.m:269 Examining keyPath 'task' for mappable content...
2012-01-31 13:24:31.570 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:104 Found a collection containing only NSNull values, considering the collection unmappable...
2012-01-31 13:24:31.571 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:279 Found unmappable value at keyPath: task
2012-01-31 13:24:31.572 RestkitDebugger[80474:15007] D restkit.object_mapping:RKObjectMapper.m:308 The following operations are in the queue: (
)
2012-01-31 13:24:31.573 RestkitDebugger[80474:15007] W restkit.object_mapping:RKObjectMapper.m:74 Adding mapping error: Could not find an object mapping for keyPath: ''
2012-01-31 13:24:31.574 RestkitDebugger[80474:15007] E restkit.network:RKObjectLoader.m:190 Encountered errors during mapping: Could not find an object mapping for keyPath: ''
2012-01-31 13:24:31.575 RestkitDebugger[80474:15007] DataManager 235 Error: Error Domain=org.restkit.RestKit.ErrorDomain Code=1001 "Could not find an object mapping for keyPath: ''" UserInfo=0x80817c0 {=RKObjectMapperKeyPath, NSLocalizedDescription=Could not find an object mapping for keyPath: ''}
2012-01-31 13:24:31.575 RestkitDebugger[80474:15007] T restkit.network.queue:RKRequestQueue.m:340 Removing request <RKManagedObjectLoader: 0x6b72270> from queue <RKRequestQueue: 0x6e58cb0 name=(null) suspended=NO requestCount=1 loadingCount=1/5>
2012-01-31 13:24:31.576 RestkitDebugger[80474:15007] T restkit.network.queue:RKRequestQueue.m:202 Loading count decreasing from 1 to 0. Firing requestQueueDidFinishLoading
2012-01-31 13:24:31.577 RestkitDebugger[80474:15007] T restkit.network.queue:RKRequestQueue.m:216 Loading count set to 0 for queue <RKRequestQueue: 0x6e58cb0 name=(null) suspended=NO requestCount=0 loadingCount=1/5>
2012-01-31 13:24:31.579 RestkitDebugger[80474:15007] T restkit.network.queue:RKRequestQueue.m:352 Decremented the loading count to 0
2012-01-31 13:24:31.580 RestkitDebugger[80474:15007] D restkit.network.queue:RKRequestQueue.m:455 Request <RKManagedObjectLoader: 0x6b72270> failed loading in queue <RKRequestQueue: 0x6e58cb0 name=(null) suspended=NO requestCount=0 loadingCount=0/5> with error: Could not find an object mapping for keyPath: ''.(Now loading 0 of 5)