Gregor mutator IndexOutOfBounds

stderr  : 15:59:47 PIT >> WARNING : Error during mutation test
stderr  : java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
stderr  : 	at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
stderr  : 	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
stderr  : 	at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266)
stderr  : 	at java.base/java.util.Objects.checkIndex(Objects.java:359)
stderr  : 	at java.base/java.util.ArrayList.get(ArrayList.java:427)
stderr  : 	at org.pitest.mutationtest.engine.gregor.GregorMutater.getMutation(GregorMutater.java:111)
stderr  : 	at org.pitest.mutationtest.execute.MutationTestWorker.processMutation(MutationTestWorker.java:93)
stderr  : 	at org.pitest.mutationtest.execute.MutationTestWorker.run(MutationTestWorker.java:79)
stderr  : 	at org.pitest.mutationtest.execute.MutationTestMinion.run(MutationTestMinion.java:97)
stderr  : 	at org.pitest.mutationtest.e15:59:47 PIT >> FINE : Exit code was - UNKxNOWN_ERROR
ecute.MutationTestMinion.main(MutationTestMinion.java:137)
15:59:47 PIT >> WARNING : Minion exited abnormally due to RUN_ERROR
15:59:47 PIT >> FINE : Setting 1 unfinished runs to RUN_ERROR state
15:59:47 PIT >> FINE : No longer able to read stream.
stdout  : Installing PIT agent
stdout  : java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
stdout  : 	at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
stdout  : 	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
stdout  : 	at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:266)
stdout  : 	at java.base/java.util.Objects.checkIndex(Objects.java:359)
stdout  : 	at java.base/java.util.ArrayList.get(ArrayList.java:427)
stdout  : 	at org.pitest.mutationtest.engine.gregor.GregorMutater.getMutation(GregorMutater.java:111)
stdout  : 	at org.pitest.mutationtest.execute.MutationTestWorker.processMutation(MutationTestWorker.java:93)
stdout  : 	at org.pitest.mutationtest.execute.MutationTestWorker.run(MutationTestWorker.java:79)
stdout  : 	at org.pitest.mutationtest.execute.MutationTestMinion.run(MutationTestMinion.java:97)
stdout  : 	at org.pitest.mutationtest.execute.MutationTestMinion.main(MutationTestMinion.java:137)
15:59:50 PIT >> FINE : Exit code was - UNKNOWN_ERROR
15:59:50 PIT >> WARNING : Minion exited abnormally due to RUN_ERROR
15:59:50 PIT >> FINE : Setting 1 unfinished runs to RUN_ERROR state