how to reproduce:
1 Have a 4k monitor without scaling turned on
2 Open a group conversation and open the sidebar
3 Switch to a 1on1 conversation

Expected behavior:
The chat and newmessageform stay in place (horizontally aligned) and a margin the size of the sidebar is added to the right of the page

Actual behavior:
The chat jumps to the right

the isMobile is not really helpful here as we want to introduce this margin only when
windowWidth - navigationWidth - sidebarWidth > 800px
800px being the size of the message component including the avatar part. We don't want to needlessly compress that.