fix: handle empty ADMIN_GROUP_THREAD_ID in settings validator

app/settings.py

@@ -1,4 +1,4 @@
-from pydantic import Field
+from pydantic import Field, field_validator
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
 
@@ -49,5 +49,12 @@ class Settings(BaseSettings):
     outline_api_prefix: str = ""
     outline_cert_sha256: str = ""
 
+    @field_validator("admin_group_thread_id", mode="before")
+    @classmethod
+    def _parse_admin_thread(cls, v):
+        if v == "" or v is None:
+            return None
+        return int(v)
+
 
 settings = Settings()