Almost cannot resize the width of system settings window

[Evan Wang]

$ system-image-cli -i
current build number: 146
device name: mako
channel: ubuntu-touch/rc-proposed/ubuntu-pd
last update: 2016-02-23 02:35:24
version version: 146
version ubuntu: 20160220
version device: 20160112
version custom: 20150929-2-vivid

Flashed the latest pd image on Mako, installed silo 10 and puritine package version 0.7
$ click list |grep puritine
com.ubuntu.puritine 0.7

Steps to reproduce:
1.Connect to BT mouse and external monitor
2. Enable desktop mode from Displays indicator -->Desktop mode
3. Open System Settings page window
4. Do not switch to maximize window, then try to adjust the width of window,
the mouse pointer will become horz mode if move mouse to the right/left edges, but only the right border can be adjusted a little, if resize the window along the diagonal only length can be adjusted.