filemanager: Opening new panes expands file tree pane

[caligari87]

QoL bug. In the original plugin, the file tree pane maintained a consistent width. In the updated version, opening or closing other panes seems to cause the file tree pane to expand to the right. Closing and re-opening the file tree returns it to normal size.

I tried commenting out the various pane resizes in the plugin lua, but the problem persisted. Not sure if the issue is with micro or the plugin.

[outfrost]

Can confirm the issue still persists. Micro 2.0.6, commit 60846f54.