The icon of external drive on launcher is invisiable

[quandan]

current build number: 54
device name: krillin
channel: ubuntu-touch/rc/bq-aquaris.en
last update: 2016-05-18 23:26:30
version version: 54
version ubuntu: 20160518.2
version device: 20160329-a9bacdb
version custom: 20160505-975-38-9

Steps:
1.Open external drive app
2.Swipe to right to open launcher and check external drive's icon

Expectation:
After step 2, the icon of external drive will be displayed on launcher correctly

Actual result:
We can see there are two dots on the both side of the icon ,but the icon's color is nearly transparent or black , which is the same color as launcher's background