[Bug] CesiumCreditSystem: NullReferenceException on exit

[Jastman]

Forum Post: https://community.cesium.com/t/crash-on-application-exit-in-cesiumcreditsystem/45952
Category: Cesium for Unity
Reported by: @MYavuzSelim

Description

Two bugs in CesiumCreditSystem.cs reported via the forum:

Bug 1 — NullReferenceException in OnDestroy()

_images is initialized in OnEnable(), but OnDestroy() accesses this._images.Count unconditionally (line ~174). If the prefab is loaded but never enabled, OnEnable() never runs, _images stays null, and OnDestroy() crashes on exit.

There is also a misplaced null check inside the loop body:

if (this._images != null)  // inside the loop — can't help here

This guard needs to wrap the entire loop, not sit inside it.

Fix: Null-guard this._images before the loop in OnDestroy().

Bug 2 — Double OnEnable() call / delegate subscribed twice

See #683

Steps to Reproduce

(To be confirmed by reporter — suspected trigger: prefab loaded without being enabled, or default credit system instantiated via GetDefaultCreditSystem())

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Opened by Cesium DevRel from forum triage.

[laurenfrederick]

Split this up into 2 issue: this and #683

[Jastman]

Editor Version: Unity 6.2 (6000.2.15f1)

User reproduced crash in both standalone builds and in the Editor.D