NERDTree resize conflict

[leon-vv]

Thanks for this amazing project!

Issue description

If a NERDTree window is open, the windows are not resized back to their correct sizes.

Steps to reproduce

Split your editor horizontally and vertically a few times and open NERDTree. Do a CtrlSF search and close the window again. The previous editor splits do not get their old sizes back.

Things about your system and environment（请在此填写你的系统信息）

field	value
os	Linux Debian testing
vim	(g)vim 7.8 including patches 1-716
backend	ag 2.2.0
locale	en_US.UTF-8

let g:ctrlsf_position = 'bottom'

Let me now if you can't reproduce this easily, and I will provide more information.