Notification displays with white background, making it invisible in some notification menus

[edluo1]

Here, the character わ should probably not be white on white (similar for か for lessons.)

Phone used is an HTC One M8, using Android version 5.0.1, aka Lollipop.

Another notification is shown to indicate that notifications on my phone often include a gray circle around the notification icon.

[s84606]

A possible fix:
https://www.dropbox.com/s/72rlts7rbmagtrc/WaniKaniMobile-1.15.7pre1-bwico01.apk
I've surrounded the two kana with a black border, so I'm not completely sure it looks good on a white background.. Please let me know if is satisfying.