Fix bugs in CLI error handling

[tsaglam]

Due to a missing null check, a null pointer exception was caused in the exception handling of the CLI class.

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "picocli.CommandLine$Model$ArgSpec.isOption()" because the return value of "picocli.CommandLine$ParameterException.getArgSpec()" is null
	at de.jplag.cli.CLI.parseOptions(CLI.java:147)
	at de.jplag.cli.CLI.main(CLI.java:77)

This occurs when a user enters a cli flag that does not exist, e.g. --foo-bar.

Furthermore, the CLI API error messages were not properly passed through. Now, the messages of wrapped exceptions are logged as well.

[sonarcloud]

Quality Gate passed for 'JPlag Plagiarism Detector'

Issues
0 New issues

Measures
0 Security Hotspots
58.3% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud