Fix minor issues with isOfInterest

[awildturtok]

Hopefully fixes

java.lang.NullPointerException: Cannot invoke "java.lang.Integer.intValue()" because the return value of "it.unimi.dsi.fastutil.objects.Object2IntMap.get(Object)" is null
        at com.bakdata.conquery.models.events.Bucket.getEntityStart(Bucket.java:110)
        at com.bakdata.conquery.models.query.queryplan.TableExportQueryPlan.execute(TableExportQueryPlan.java:95)
        at com.bakdata.conquery.models.query.QueryJob.get(QueryJob.java:30)
        at com.bakdata.conquery.models.query.QueryJob.get(QueryJob.java:12)
        at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(Unknown Source)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.base/java.lang.Thread.run(Unknown Source)