NPE on second attempt to build

Greetings to everybody! I strive to port Groupoid Infinity library to Arend!

For now we have several issues:

1. Prelude.ard isn’t compilng;
2. NPE on second build attempt without removal of lib/.output.

Reproduce:

$ git clone https://github.com/JetBrains/Arend.git
$ ./gradlew
$ ./gradlew jarDep
$ java -jar ./build/libs/arend.jar -s lib

Results:

--- Typechecking \default ---
[ERROR] Prelude:14:9: 'Nat.zero' is not a constructor of data type Nat
  In: zero
  While processing: Nat.-
[ERROR] Prelude:15:16: 'Nat.zero' is not a constructor of data type Nat
  In: zero
  While processing: Nat.-
[ERROR] Prelude:33:5: Coverage check failed
  In: \func inProp {A : \Prop} : \Pi (a a' : A) -> a = a'
  While processing: Path.inProp
[WARNING] Prelude:41:5: This clause is redundant
  In: | path f, i => f i
  While processing: @
[ERROR] Prelude:43:1: Some clauses are missing
  right
  In: \func coe (A : I -> \Type) (a : A left) (i : I) : A i \elim i
          | left => a
  While processing: coe
[✗] Prelude
Number of modules with errors: 1
--- Done ---

If I make compilation second time

$ java -jar ./build/libs/arend.jar -s lib

without erasing lib/.output I get following:

--- Typechecking \default ---
Exception in thread "main" java.lang.NullPointerException

[valis]

I’ve committed it 12 hours ago, but pushed only 5 minutes ago.

[5HT]

Thanks a lot. Will try to port following module to Arend: https://github.com/groupoid/infinity/blob/master/priv/bundle.ctt