[FIX] mail: strip comments when inlining
[FIX] mail: strip comments when inlining

When an unread message contains conditional html statements, clicking on
the discuss tray icon produces a JS traceback. This is due to
`node.tagName` being undefined.

When inlining, there is no need for these comments.

opw-1829641

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo