[BUG] Placeholder size is different on startup #1079
Description
Description of the error
When I start MDANSE, the placeholder takes up a specific amount of space in the 3D viewer. When I load a trajectory and then delete it, the placeholder is reloaded, but the size of the placeholder is much smaller.
Describe the expected result
The placeholder should be the same size on reload. On the first start, it should be the size it is on the reload.
Additional details
