java.lang.NullPointerException while installing pdffigures2

I installed Scala and tried to install pdffigures2, but it failed:

```
richard@pito  ~/src  rm -rf pdffigures*
richard@pito  ~/src  git clone https://github.com/allenai/pdffigures2
Cloning into 'pdffigures2'...
remote: Enumerating objects: 392, done.
remote: Total 392 (delta 0), reused 0 (delta 0), pack-reused 392
Receiving objects: 100% (392/392), 6.43 MiB | 2.48 MiB/s, done.
Resolving deltas: 100% (111/111), done.
richard@pito  ~/src  cd pdffigures2
richard@pito  ~/src/pdffigures2   master  sbt assembly
[info] Loading project definition from /home/richard/src/pdffigures2/project
[info] Updating {file:/home/richard/src/pdffigures2/project/}pdffigures2-build...
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by sbt.ivyint.ErrorMessageAuthenticator$ (file:/home/richard/.sbt/boot/scala-2.10.4/org.scala-sbt/sbt/0.13.8/ivy-0.13.8.jar) to field java.net.Authenticator.theAuthenticator
WARNING: Please consider reporting this to the maintainers of sbt.ivyint.ErrorMessageAuthenticator$
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
java.lang.NullPointerException
at java.base/java.util.regex.Matcher.getTextLength(Matcher.java:1769)
at java.base/java.util.regex.Matcher.reset(Matcher.java:416)
at java.base/java.util.regex.Matcher.(Matcher.java:253)
at java.base/java.util.regex.Pattern.matcher(Pattern.java:1130)
at java.base/java.util.regex.Pattern.split(Pattern.java:1249)
at java.base/java.util.regex.Pattern.split(Pattern.java:1322)
at sbt.IO$.pathSplit(IO.scala:744)
at sbt.IO$.parseClasspath(IO.scala:859)
at sbt.compiler.CompilerArguments.extClasspath(CompilerArguments.scala:62)
at sbt.compiler.MixedAnalyzingCompiler$.withBootclasspath(MixedAnalyzingCompiler.scala:189)
at sbt.compiler.MixedAnalyzingCompiler$.searchClasspathAndLookup(MixedAnalyzingCompiler.scala:167)
at sbt.compiler.MixedAnalyzingCompiler$.apply(MixedAnalyzingCompiler.scala:177)
at sbt.compiler.IC$.incrementalCompile(IncrementalCompiler.scala:138)
at sbt.Compiler$.compile(Compiler.scala:128)
at sbt.Compiler$.compile(Compiler.scala:114)
at sbt.Defaults$.sbt$Defaults$$compileIncrementalTaskImpl(Defaults.scala:814)
at sbt.Defaults$$anonfun$compileIncrementalTask$1.apply(Defaults.scala:805)
at sbt.Defaults$$anonfun$compileIncrementalTask$1.apply(Defaults.scala:803)
at scala.Function1$$anonfun$compose$1.apply(Function1.scala:47)
at sbt.$tilde$greater$$anonfun$$u2219$1.apply(TypeFunctions.scala:40)
at sbt.std.Transform$$anon$4.work(System.scala:63)
at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:226)
at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:226)
at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:17)
at sbt.Execute.work(Execute.scala:235)
at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:226)
at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:226)
at sbt.ConcurrentRestrictions$$anon$4$$anonfun$1.apply(ConcurrentRestrictions.scala:159)
at sbt.CompletionService$$anon$2.call(CompletionService.scala:28)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:514)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:844)
[error] (compile:compileIncremental) java.lang.NullPointerException
Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? r
[info] Loading project definition from /home/richard/src/pdffigures2/project
java.lang.NullPointerException
at java.base/java.util.regex.Matcher.getTextLength(Matcher.java:1769)
at java.base/java.util.regex.Matcher.reset(Matcher.java:416)
at java.base/java.util.regex.Matcher.(Matcher.java:253)
at java.base/java.util.regex.Pattern.matcher(Pattern.java:1130)
at java.base/java.util.regex.Pattern.split(Pattern.java:1249)
at java.base/java.util.regex.Pattern.split(Pattern.java:1322)
at sbt.IO$.pathSplit(IO.scala:744)
at sbt.IO$.parseClasspath(IO.scala:859)
at sbt.compiler.CompilerArguments.extClasspath(CompilerArguments.scala:62)
at sbt.compiler.MixedAnalyzingCompiler$.withBootclasspath(MixedAnalyzingCompiler.scala:189)
at sbt.compiler.MixedAnalyzingCompiler$.searchClasspathAndLookup(MixedAnalyzingCompiler.scala:167)
at sbt.compiler.MixedAnalyzingCompiler$.apply(MixedAnalyzingCompiler.scala:177)
at sbt.compiler.IC$.incrementalCompile(IncrementalCompiler.scala:138)
at sbt.Compiler$.compile(Compiler.scala:128)
at sbt.Compiler$.compile(Compiler.scala:114)
at sbt.Defaults$.sbt$Defaults$$compileIncrementalTaskImpl(Defaults.scala:814)
at sbt.Defaults$$anonfun$compileIncrementalTask$1.apply(Defaults.scala:805)
at sbt.Defaults$$anonfun$compileIncrementalTask$1.apply(Defaults.scala:803)
at scala.Function1$$anonfun$compose$1.apply(Function1.scala:47)
at sbt.$tilde$greater$$anonfun$$u2219$1.apply(TypeFunctions.scala:40)
at sbt.std.Transform$$anon$4.work(System.scala:63)
at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:226)
at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:226)
at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:17)
at sbt.Execute.work(Execute.scala:235)
at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:226)
at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:226)
at sbt.ConcurrentRestrictions$$anon$4$$anonfun$1.apply(ConcurrentRestrictions.scala:159)
at sbt.CompletionService$$anon$2.call(CompletionService.scala:28)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:514)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:844)
[error] (compile:compileIncremental) java.lang.NullPointerException
Project loading failed: (r)etry, (q)uit, (l)ast, or (i)gnore? i
[warn] Ignoring load failure: no project loaded.
[error] Not a valid command: assembly
[error] assembly
[error] ^
```

I also tried to `sbt compile` as per https://github.com/allenai/pdffigures2/issues/16#issuecomment-331049926