Adding a module to a group via double-click is not working anymore

[TimPietrusky]

Operating system and application version

• OS: macOS & Ubuntu 16.04
• Version: 3.7.0

Describe the bug
When I want to add a module to a group using a double click nothing happens.

To Reproduce
Steps to reproduce the behavior:

1. Double click on any module
2. See that nothing happens
3. Click on any group to focus it
4. Do 1. again
5. See 2. again

Expected behavior
The module is added to the active group.

[2xAA]

My changes in #480 broke this 😒