Workspace Explorer background doesn't follow Colours setting

[JasonRivers]

Describe the issue you are having

Workspace explorer doesn't follow the colours setting making text unreadable, see screenshot:

Did you connect to an already running interpreter or start the interpreter from RIDE?

N/A

How do you reproduce the issue?

Set colours in preferences to Francisco Goya & open Workspace Explorer

Paste the contents of Help → About (Shift+F1)

IDE:
  Version: 4.0.2841
  Platform: Linux x86_64
  Date: 2017-06-26 15:15:15 +0200
  Git commit: 71bccd84abb4404fa41518ea362cbf7fccc5e054
  Preferences:{
    "colourScheme":"Francisco Goya",
    "favs":"[{\"type\":\"start\",\"ssh_auth_type\":\"pass\",\"ssh_tnl_auth_type\":\"pass\",\"exe\":\"/opt/mdyalog/16.0/64/unicode/mapl\",\"name\":\"172.17.0.3\",\"host\":\"172.17.0.3\"},{\"ssh_auth_type\":\"pass\",\"ssh_tnl_auth_type\":\"pass\",\"name\":\"MKPI\",\"host\":\"10.0.60.127\"},{\"ssh_auth_type\":\"pass\",\"ssh_tnl_auth_type\":\"pass\",\"name\":\"localhost\",\"host\":\"localhost\",\"type\":\"start\",\"exe\":\"/opt/mdyalog/16.0/64/unicode/mapl\",\"port\":\"9999\"}]",
    "kbdLocale":"en_GB",
    "keys":"{\"WSE\":[\"Shift-Ctrl-E\"]}",
    "selectedExe":"/opt/mdyalog/15.0/64/unicode/mapl",
    "wse":"1",
    "zoom":"-2"
  }

Interpreter:
  Version: 16.0.30142
  Platform: Linux-64
  Edition: Unicode/64
  Date: Jun 19 2017 at 02:08:38

[e9gille]

fixed in 4.1