Object reference not set to an instance of an object.

[WhiteNightAWA]

Fun things happened. When I trying to pack up akaruiyagi's songs, it said

Import target: Archive file
Exception:
Object reference not set to an instance of an object

(while importing it in the game)

index.yml of the pack

- directory: akaruiyagi_akaruiyagi
  identifier: com.akaruiyagi.akaruiyagi.pack
  settingsFile: pack.yml
  version: 0
  type: pack
- directory: paqqinremix
  identifier: akaruiyagi.paqqinremix
  settingsFile: project.arcproj
  type: level
- directory: apocaliptix
  identifier: akaruiyagi.apocaliptix
  settingsFile: project.arcproj
  type: level
- directory: emergence
  identifier: akaruiyagi.emergence
  settingsFile: project.arcproj
  type: level
- directory: transmission
  identifier: akaruiyagi.transmission
  settingsFile: project.arcproj
  type: level
- directory: mayhem
  identifier: akaruiyagi.mayhem
  settingsFile: project.arcproj
  type: level
- directory: finalhope
  identifier: akaruiyagi.finalhope
  settingsFile: project.arcproj
  type: level

pack.yml

imagePath: pack.png
levelIdentifiers:
- akaruiyagi.paqqinremix
- akaruiyagi.apocaliptix
- akaruiyagi.emergence
- akaruiyagi.transmission
- akaruiyagi.mayhem
- akaruiyagi.finalhope
packName: akaruiyagi

these look quite normal with others... still finding problems.

[WhiteNightAWA]

structure of that pack:

[WhiteNightAWA]

Fortunately, this program still work normal for other song.