feat:async blend sub node of list

Pod/Classes/Shader/DoricListNode.m

@@ -182,11 +182,17 @@ - (NSDictionary *)itemModelAt:(NSUInteger)position {
             NSUInteger pos = position + idx;
             self.itemViewIds[@(pos)] = thisViewId;
         }];
+        if (array.count > 0) {
             return array[0];
+        } else {
+            return nil;
+        }
     }
 }
 
 - (void)blendSubNode:(NSDictionary *)subModel {
+    ///Here async blend sub node because the item count need to be applied first.
+    dispatch_async(dispatch_get_main_queue(), ^{
         NSString *viewId = subModel[@"id"];
         DoricViewNode *viewNode = [self subNodeWithViewId:viewId];
         if (viewNode) {
@@ -205,6 +211,8 @@ - (void)blendSubNode:(NSDictionary *)subModel {
                 }];
             }
         }];
+    });
+
 }
 
 - (void)callItem:(NSUInteger)position height:(CGFloat)height {