[18.0][BUG] web_chatter_position pdf preview glitch on sided mode

[houssine78]

Module

web_chatter_position

Describe the bug

On version 18.0 there is a glitch rendering when previewing a pdf in the sided/responsive mode for the chatter.

In version 17.0 it was displaying the pdf in the chatter on sided mode.
In version 18.0 the pdf is displayed in a pop up window which is the same behaviour that the below mode for the chatter on version 17.0

To Reproduce

Affected versions: 18.0

Steps to reproduce the behavior:

1. on runbot, on the web repository
2. in the user preference set the chatter position to sided
3. open a form on any model with chatter on it (sale.order, account.move,...)
4. in the chatter attach a pdf to the record
5. if the attachment panel is not displayed click on the paperclip icon
6. move the mouse cursor to the pdf document
7. the cursor show up as a magnifying glass
8. click on the pdf
9. the pdf open in a popup window.

Expected behavior
Having the pdf showing up in the right sided panel (the chatter panel in sided mode) as it does for the version 17.0