Reproduction steps:
1. Open the attached project "Texture2DArray.zip"
2. In the Project's Build Settings ensure that the Build Target is set to iOS
3. Select "t_mountain_combined_n_02.tga" in the Project Window
4. In the Inspector set the "Texture Shape" to "2D Array"

Reproducible with: 2020.3.27f1, 2021.2.0a11
Not reproducible with: 2019.4.35f1 (Texture Shape 2D Array not available)

First lines of the stack trace:
#0 0x000001046e2940 in StackAllocator::TryDeallocate(void)
#1 0x000001046d8884 in MemoryManager::Deallocate(void, MemLabelId const&, char const, int)
#2 0x00000105aa97f3 in CompressWithPVRTexTool(ExternalToolCompressionParams, ExternalToolCompressionError)
#3 0x00000105aa777f in CompressSingleImageTexture(ImageReference&, TextureFormat, TextureUsageMode, int, bool, bool, bool, unsigned char, Texture const)
#4 0x00000105aaaee2 in CompressTexture2DArray(Texture2DArray&, TextureFormat, int, bool, bool)
#5 0x00000105a875f7 in TextureGenerator::GenerateTexture(TextureGlobalSettingsProvider&, TextureGenerationSettings const&, TextureGenerationOutput&)