existing `executionInfo/stdout.txt` causes titanic model to crash

[kevinchern]

Problem: running titanic model crashes when the output directory has the file executionInfo/stdout.txt.

Steps to reproduce:

cd /tmp/  # optional
git clone git@github.com:UBC-Stat-ML/blangDemos.git
cd blangDemos
./gradlew installDist
mkdir -p BLAHBLAH/executionInfo
touch BLAHBLAH/executionInfo/stdout.txt
./build/install/blangDemos/bin/blangDemos titanic --experimentConfigs.uniqueExperimentDirectoryName BLAHBLAH --engine.initialization FORWARD --engine.nThreads Fixed --engine.random 8

Surprisingly, it does not get an error with --engine.random 9 or 7.

Appending --help also causes a crash, i.e.,

./build/install/blangDemos/bin/blangDemos titanic --experimentConfigs.uniqueExperimentDirectoryName BLAHBLAH --help

Note: data source data/titanic/titanic-covariates.csv does not contain column parameters --- treating as missing
Exception in thread "main" java.lang.NullPointerException
        at blang.inits.experiments.Experiment.cleanEmptyResultFolder(Experiment.java:371)
        at blang.inits.experiments.Experiment.start(Experiment.java:148)
        at blang.runtime.Runner.start(Runner.java:196)
        at demos.Main.main(Main.java:40)