message: Log android error if model couldn't be loaded from asset manager
diff: #include <string>
  #include <fstream>
  #include <vector>
  -#include <map>
  #include "vulkan/vulkan.h"
  @@ -167,6 +166,10 @@ namespace vks
  // So they need to be loaded via the asset manager
  AAsset* asset = AAssetManager_open(androidApp->activity->assetManager, filename.c_str(), AASSET_MODE_STREAMING);
  + if (!asset) {
  + LOGE("Could not load mesh from \"%s\"!", filename.c_str());
  + return false;
  + }
  assert(asset);
  size_t size = AAsset_getLength(asset);
  