Sidebar does not open if body-text is not wide enough

Hi! Thank you for the great package, I've found it very useful so far. I've come across a rather strange issue however.

I like to use [olivetti-mode](https://github.com/rnkn/olivetti) to make org-buffers somewhat "narrower" (different than narrowing the buffer) to make it nicer to write in, like so

However, when this is active, neither `org-sidebar` nor `org-sidebar-toggle` do anything. It does run, as it toggles `truncate-lines`
If I turn it off it works just as you'd expect.

The issue does not seem to be with any specific olivetti-mode implementation, but with the fact that it changes the width of the margins/fringes/text. In fact, when I set the character width of olivetti-mode > 110 characters, the sidebar appears.

Do you know how I could fix this? I've tried to understand why this happens by looking at `org-sidebar.el`, but no luck so far. There do seem to be checks for the narrowness of buffers, but if I understand correctly this has little to do with the width of the buffer-text.

Thanks in advance!

PS. Amazing that you managed to split side-windows, [I struggled for a long time to do so](https://emacs.stackexchange.com/questions/63001/how-do-i-split-a-side-window) and eventually gave up, but this made me realize it's possible!