How to reproduce:
1. Open the attached user project

Result - Crash occurs on:

========== OUTPUTING STACK TRACE ==================

0x000000014189CF68 (Unity) AudioEffectInternalDescription::AudioEffectInternalDescription
0x000000014189F08D (Unity) GetAudioEffectDefinitions
0x00000001411DFA24 (Unity) MixerEffectDefinitions_CUSTOM_GetAudioEffectNames
0x000000005708F38A (Mono JIT Code) (wrapper managed-to-native) UnityEditor.Audio.MixerEffectDefinitions:GetAudioEffectNames ()
0x000000005708DE1D (Mono JIT Code) [C:\buildslave\unity\build\Editor\Mono\Audio\Mixer\AudioMixerDescription.cs:74] UnityEditor.Audio.MixerEffectDefinitions:Refresh

Reproducible with - 2017.3.0b2, 2017.2.0f2, 2017.1.1p3, 5.6.3p4

Note - The bug in Audio Spatializer SDK that causes the crash is that when you create a spatializer, per your Native Audio SDK, you need to create a enum which lists the parameters you can set. If you add an enum, but then do not ALSO add a corresponding line to the InternalRegisterEffectDefinition function calling "RegisterParameter" for that enum value, the crash occurs