JOC Cockpit shows black background color for Firefox

Current Situation

• JOC Cockpit shows a black background with the tree panel and the view panel when hovering with the mouse.
• see attached screenshot.
• This problem can be observed with Firefox e.g. release 59.0.2 and 60.0.1 using the "white" theme in JOC Cockpit. This problem does not occur with current Chrome versions.

Desired Behavior

• JOC Cockpit should work with current Firefox versions

Maintainer Notes

• This issue is not related to JOC Cockpit, but to Firefox.
• Deactivating graphics hardware acceleration might resolve the issue, see https://support.mozilla.org/de/questions/1123638