Particles are created when paused but are never freed, leading to performance drop over time

[Calinou]

• Version and build: Git https://github.com/redeclipse/base/commit/25a03f0cd55032290245b89bd42f459abbd667af
• Related discussion: N/A
• Observation: Particles are created while paused but are never destroyed, which makes performance tank if you pause for more than a few seconds.
• Expected result: New particles shouldn't be created while paused.
• How to reproduce: In offline practice, pause the game by pressing the Pause key or enter /pausegame 1 in the console. This may be easier to reproduce if you do it while airborne, so that particles are continuously emitted by your player model. That said, this may occur even if you aren't airborne due to other players in view being airborne when pausing.

If you rotate while paused, you'll notice something like this occurring: