Steps to repro:
1.Download the latest AudioNativePlugin project from bitbucket
2. Uncompress and open with the b21 build

Unity crashes with the following stack trace:

Receiving unhandled NULL exception
Launching bug reporter
Obtained 94 stack frames.
#0 0x0000010122d3bd in AllocationRootReference::~AllocationRootReference()
#1 0x0000010122d71c in AllocationRootReference::Release()
#2 0x00000100e45034 in MemoryManager::Reallocate(void, unsigned long, int, MemLabelId const&, int, char const, int)
#3 0x00000100e44b6c in realloc_internal(void, unsigned long, int, MemLabelId const&, int, char const, int)
#4 0x0000010122e02b in MemoryProfiler::PushAllocationRoot(void, BaseAllocator, bool)
#5 0x00000100e3f274 in push_allocation_root(void, BaseAllocator, bool)
#6 0x0000010125d280 in PersistentManager::PostLoadStreamNameSpace(StreamNameSpace&, int)
#7 0x00000101253cd8 in PersistentManager::GetStreamNameSpaceInternal(int)
#8 0x00000101252808 in PersistentManager::GetSerializedFileInternalIfObjectAvailable(int, long long)
#9 0x00000101259af1 in PersistentManager::ReadObjectThreaded(int)
#10 0x00000101257f43 in PersistentManager::ReadObject(int, AwakeFromLoadMode)
#11 0x00000101935d83 in PPtr<AudioMixerEffectController>::operator*() const