Fix: Set default value in FindInterface._inheritance_inited to avoid …

…AttributeError in _add_class_id_filter method (#935)

Fixed error raised when in "FindInterface._add_class_id_filter" method (line 458) when a attempt to acess the value from "FindInterface._inheritance_inited"

beanie/odm/interfaces/find.py

@@ -39,7 +39,7 @@ class FindInterface:
  _find_one_query_class: ClassVar[Type] = FindOne
  _find_many_query_class: ClassVar[Type] = FindMany
 
- _inheritance_inited: bool
+ _inheritance_inited: bool = False
  _class_id: ClassVar[Optional[str]]
  _children: ClassVar[Dict[str, Type]]