Fix type error in update command - handle None package name

Author: codegen-sh[bot]

src/codegen/cli/commands/update/main.py

@@ -44,7 +44,8 @@ def update(
         rich.print("[red]Error:[/red] Cannot specify both --list and --version")
         raise typer.Exit(1)
 
-    package_info = distribution(codegen.__package__)
+    package_name = codegen.__package__ or "codegen"
+    package_info = distribution(package_name)
     current_version = Version(package_info.version)
 
     if list_: