LogicSim builds but doesn't run

[pracplayopen]

ATTEMPTED:

$ git clone https://github.com/codepiet/LogicSim3
$ cd LogicSim3
$ ant
Buildfile: /home/ppo/work/src/LogicSim3/build.xml

clean:
   [delete] Deleting directory /home/ppo/work/src/LogicSim3/build
   [delete] Deleting directory /home/ppo/work/src/LogicSim3/dist
   [delete] Deleting: /home/ppo/work/src/LogicSim3/LogicSim.jar

compile:
    [mkdir] Created dir: /home/ppo/work/src/LogicSim3/build/classes
    [javac] /home/ppo/work/src/LogicSim3/build.xml:23: warning: 'includeantruntime' was not set, defaulting to build.sysclasspath=last; set to false for repeatable builds
    [javac] Compiling 80 source files to /home/ppo/work/src/LogicSim3/build/classes
    [javac] warning: [options] bootstrap class path not set in conjunction with -source 8
    [javac] 1 warning

jar:
    [mkdir] Created dir: /home/ppo/work/src/LogicSim3/build/jar
     [copy] Copying 20 files to /home/ppo/work/src/LogicSim3/build/classes/logicsim/images
      [jar] Building jar: /home/ppo/work/src/LogicSim3/build/jar/LogicSim.jar

run:
     [copy] Copying 1 file to /home/ppo/work/src/LogicSim3
     [java] Exception in thread "main" java.lang.NullPointerException
     [java] 	at logicsim.GateLoaderHelper.getClassesOutsideJar(Unknown Source)
     [java] 	at logicsim.GateLoaderHelper.getClasses(Unknown Source)
     [java] 	at logicsim.App.initializeGateCategories(Unknown Source)
     [java] 	at logicsim.App.<init>(Unknown Source)
     [java] 	at logicsim.App.main(Unknown Source)
     [java] Java Result: 1

main:

BUILD SUCCESSFUL
Total time: 3 seconds

So build works w/an error during run target.
If run manually same error is received:

$ java -jar LogicSim.jar 
Exception in thread "main" java.lang.NullPointerException
	at logicsim.GateLoaderHelper.getClassesOutsideJar(Unknown Source)
	at logicsim.GateLoaderHelper.getClasses(Unknown Source)
	at logicsim.App.initializeGateCategories(Unknown Source)
	at logicsim.App.<init>(Unknown Source)
	at logicsim.App.main(Unknown Source)

Expected result... logicsim should start and run.
Instead, the error above is received.

I also downloaded the 'release' source and the same error happens with it.

system information:

$ java -version
openjdk version "11.0.23" 2024-04-16
OpenJDK Runtime Environment (build 11.0.23+9-post-Ubuntu-1ubuntu122.04.1)
OpenJDK 64-Bit Server VM (build 11.0.23+9-post-Ubuntu-1ubuntu122.04.1, mixed mode, sharing)
$ ant -version
Apache Ant(TM) version 1.10.12