[FIX] mail: prevent traceback on attachment unlink

Due to asynchronous rendering, the attachment template can be rendered
when its attachment is undefined, this was causing an issue with an
unguarded getter call that was attempting to access the attachment.

This commit fixes this issue.

opw-2457983

closes odoo/odoo#65992

X-original-commit: 33802c65c3e8d04c54de3fca5903f66b34b9d13a
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/components/attachment/attachment.xml

@@ -6,7 +6,7 @@
             t-att-class="{
                 'o-downloadable': props.isDownloadable,
                 'o-editable': props.isEditable,
-                'o-has-card-details': detailsMode === 'card',
+                'o-has-card-details': attachment and detailsMode === 'card',
                 'o-isUploading': attachment and attachment.isUploading,
                 'o-viewable': attachment and attachment.isViewable,
             }" t-att-title="attachment ? attachment.displayName : undefined" t-att-data-attachment-local-id="attachment ? attachment.localId : undefined"