[FIX] website_theme_install: avoid crashing if install_filename not in context

closes odoo/odoo#38888

X-original-commit: 28dce415
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>

addons/website_theme_install/models/theme_models.py

@@ -14,6 +14,8 @@ class ThemeView(models.Model):
     _description = 'Theme UI View'
 
     def compute_arch_fs(self):
+        if 'install_filename' not in self._context:
+            return ''
         path_info = get_resource_from_path(self._context['install_filename'])
         if path_info:
             return '/'.join(path_info[0:2])