message: Make sure to set refData to NULL whenever it's released
diff: @@ -501,7 +501,10 @@ void WrappedVulkan::vkFreeMemory(VkDevice device, VkDeviceMemory memory,
  {
  // there is an implicit unmap on free, so make sure to tidy up
  if(wrapped->record->memMapState && wrapped->record->memMapState->refData)
  + {
  Serialiser::FreeAlignedBuffer(wrapped->record->memMapState->refData);
  + wrapped->record->memMapState->refData = NULL;
  + }
  {
  SCOPED_LOCK(m_CoherentMapsLock);
  @@ -668,6 +671,7 @@ void WrappedVulkan::vkUnmapMemory(VkDevice device, VkDeviceMemory mem)
  }
  Serialiser::FreeAlignedBuffer(state.refData);
  + state.refData = NULL;
  if(state.mapCoherent)
  {
  