ERPNEXT SYNC Error : 'dict' object has no attribute 'extend'

When i was run this bench frappe --sync_all Command

Error : ‘dict’ object has no attribute ‘extend’
How can i solve this.

Traceback (most recent call last):
  File "/home/ratul/university/env/bin/frappe", line 9, in <module>
    load_entry_point('frappe==5.0.0b0', 'console_scripts', 'frappe')()
  File "/home/ratul/university/apps/frappe/frappe/cli.py", line 53, in main
  File "/home/ratul/university/apps/frappe/frappe/cli.py", line 83, in run
  File "/home/ratul/university/apps/frappe/frappe/cli.py", line 67, in new_fn
  File "/home/ratul/university/apps/frappe/frappe/cli.py", line 470, in sync_all
  File "/home/ratul/university/apps/frappe/frappe/model/sync.py", line 16, in sync_all
    block_user(True)
  File "/home/ratul/university/apps/frappe/frappe/modules/patch_handler.py", line 100, in block_user
    frappe.db.set_global('__session_status', block and 'stop' or None)
  File "/home/ratul/university/apps/frappe/frappe/database.py", line 617, in set_global
    self.set_default(key, val, user)
  File "/home/ratul/university/apps/frappe/frappe/database.py", line 625, in set_default
    frappe.defaults.set_default(key, val, parent, parenttype)
  File "/home/ratul/university/apps/frappe/frappe/defaults.py", line 87, in set_default
    add_default(key, value, parent)
  File "/home/ratul/university/apps/frappe/frappe/defaults.py", line 98, in add_default
    d.insert(ignore_permissions=True)
  File "/home/ratul/university/apps/frappe/frappe/model/document.py", line 170, in insert
    self.run_method("before_insert")
  File "/home/ratul/university/apps/frappe/frappe/model/document.py", line 507, in run_method
    return Document.hook(fn)(self, *args, **kwargs)
  File "/home/ratul/university/apps/frappe/frappe/model/document.py", line 615, in composer
    doc_events = frappe.get_hooks("doc_events", {})
  File "/home/ratul/university/apps/frappe/frappe/__init__.py", line 663, in get_hooks
    hooks = _dict(cache().get_value("app_hooks", load_app_hooks))
  File "/home/ratul/university/apps/frappe/frappe/utils/redis_wrapper.py", line 47, in get_value
    val = generator()
  File "/home/ratul/university/apps/frappe/frappe/__init__.py", line 643, in load_app_hooks
    append_hook(hooks, key, getattr(app_hooks, key))
  File "/home/ratul/university/apps/frappe/frappe/__init__.py", line 652, in append_hook
    append_to_list(target, key, value)
  File "/home/ratul/university/apps/frappe/frappe/__init__.py", line 658, in append_to_list
    target[key].extend(value)
AttributeError: 'dict' object has no attribute 'extend'

Seems like an issue with one your custom hooks.py