Milestones/sessions for all groups are not visible in group filtered "overview" graph

[F0urchette]

Description

If milestones or sessions are added for "All" TP groups, filtering the overview graph with a TP group will hide them.

Steps to reproduce

• Create a milestone/session with "All" as TP group
• Filter the overview graph with a specific TP group

Actual result

The newly added milestone/session for all groups is not showing.

Expected result

The newly added milestone/session for all groups is showing.