Fix VTK actor leak due to incorrect cleanup guard in e-field visualization

[suhr25]

Summary

Fixes a renderer cleanup issue in viewer_volume.py affecting MaxEfieldActor(), CoGEfieldActor(), and InitEfield().
Previously, actors were not always removed due to a coupled and condition, which could skip cleanup if one actor was None. This could leave valid actors in the renderer without Python references, causing a VTK-side memory/rendering leak.

Fix

• Independent cleanup: Replaced paired checks with per-actor guards.
• Lifecycle reset: Added = None after RemoveActor() to release references.
• Consistency: Aligned with the existing pattern used for edge_actor.

Before

if self.max_efield_vector and self.ball_max_vector is not None:
    self.ren.RemoveActor(self.max_efield_vector)
    self.ren.RemoveActor(self.ball_max_vector)

After

if self.max_efield_vector is not None:
    self.ren.RemoveActor(self.max_efield_vector)
    self.max_efield_vector = None

if self.ball_max_vector is not None:
    self.ren.RemoveActor(self.ball_max_vector)
    self.ball_max_vector = None

Verification

Repeated InitEfield() calls keep actor count stable (self.ren.GetActors().GetNumberOfItems()), with no memory growth or visual changes.

[suhr25]

Hi @paulojamorim,
Fixes a cleanup issue where actors weren’t removed if one of the pair was None, causing accumulation over time.
Now each actor is removed independently and properly reset, preventing renderer and memory growth.

[suhr25]

Hi @sotodela @paulojamorim,

Just following up on this PR when you have a moment.
Thanks!

[suhr25]

Hi @sotodela @paulojamorim,
Can you please review this PR.
Thanks!

[suhr25]

Hi @sotodela @paulojamorim,
Just a follow up message
Kindly review this PR.
Thanks!

[suhr25]

Hi @sotodela @paulojamorim,
Just a follow up message
Please review this PR.
Thanks!