Make mypy happy

setup.py

@@ -962,7 +962,7 @@ def build_static_kittens(
 ) -> str:
     if args.skip_building_kitten:
         print('Skipping building of the kitten binary because of a command line option. Build is incomplete', file=sys.stderr)
-        return
+        return ''
     sys.stdout.flush()
     sys.stderr.flush()
     go = shutil.which('go')
@@ -1459,6 +1459,8 @@ def create_macos_bundle_gunk(dest: str, for_freeze: bool, args: Options) -> str:
     create_macos_app_icon(os.path.join(ddir, 'Contents', 'Resources'))
     if not for_freeze:
         kitten_exe = build_static_kittens(args, launcher_dir=os.path.dirname(kitty_exe))
+        if not kitten_exe:
+            raise SystemExit('kitten not built cannot create macOS bundle')
         os.symlink(os.path.relpath(kitten_exe, os.path.dirname(in_src_launcher)),
                    os.path.join(os.path.dirname(in_src_launcher), os.path.basename(kitten_exe)))
     return str(kitty_exe)