fix: 修复迁移应用时(组织下只有根节点，同步后的应用资产没有设置节点的问题)

apps/assets/migrations/0098_auto_20220430_2126.py

@@ -20,6 +20,7 @@ def get_prop_name_id(apps, app, category):
 
 
 def migrate_database_to_asset(apps, *args):
+    node_model = apps.get_model('assets', 'Node')
     app_model = apps.get_model('applications', 'Application')
     db_model = apps.get_model('assets', 'Database')
     platform_model = apps.get_model('assets', 'Platform')
@@ -84,11 +85,18 @@ def create_app_nodes(apps, org_id):
     node_keys = node_model.objects.filter(org_id=org_id) \
         .filter(key__regex=child_pattern) \
         .values_list('key', flat=True)
-    if not node_keys:
-        return
-    node_key_split = [key.split(':') for key in node_keys]
-    next_value = max([int(k[1]) for k in node_key_split]) + 1
-    parent_key = node_key_split[0][0]
+    if node_keys:
+        node_key_split = [key.split(':') for key in node_keys]
+        next_value = max([int(k[1]) for k in node_key_split]) + 1
+        parent_key = node_key_split[0][0]
+    else:
+        root_node = node_model.objects.filter(org_id=org_id)\
+            .filter(parent_key='', key__regex=r'^[0-9]+$').exclude(key__startswith='-').first()
+        if not root_node:
+            return
+        parent_key = root_node.key
+        next_value = 0
+
     next_key = '{}:{}'.format(parent_key, next_value)
     name = 'Apps'
     parent = node_model.objects.get(key=parent_key)