An exception is thrown when no results are generated due to a division by zero in JavaParserMain.scala at line 60

Start in javaparser/src/main/scala/com/virtuslab/semanticgraphs/javaparser/JavaParserMain.scala at line 60, where the failure percentage is calculated, and trace how generateSemanticGraphFiles is called from ScgCli.scala. Handle the zero-results case with a clear message instead of an ArithmeticException, and verify that normal result generation still reports its percentage.

In this file, there is an instruction that shows the percentage of failed results compared to the total number of results generated. However, the total can be zero. It would be really helpful to have a message that says that no results have been generated, as it can be quite confusing to encounter a "dividing by zero" exception (see below) when using the tool for the first time.

java.lang.ArithmeticException: / by zero
	at com.virtuslab.semanticgraphs.javaparser.JavaParserMain$.generateSemanticGraphFiles(JavaParserMain.scala:60)
	at org.virtuslab.semanticgraphs.analytics.cli.ScgCli.generate(ScgCli.scala:59)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at picocli.CommandLine.executeUserObject(CommandLine.java:2066)
	at picocli.CommandLine.access$1500(CommandLine.java:148)
	at picocli.CommandLine$RunLast.executeUserObjectOfLastSubcommandWithSameParent(CommandLine.java:2461)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:2453)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:2415)
	at picocli.CommandLine$AbstractParseResultHandler.execute(CommandLine.java:2273)
	at picocli.CommandLine$RunLast.execute(CommandLine.java:2417)
	at picocli.CommandLine.execute(CommandLine.java:2170)
	at org.virtuslab.semanticgraphs.analytics.cli.ScgCli$.main(ScgCli.scala:335)
	at org.virtuslab.semanticgraphs.analytics.cli.ScgCli.main(ScgCli.scala)