PrefService barfs with some inputs

[ctrueden]

In Fiji, run the Widgets JavaScript script template with default values (all zeroes) prior to any persistence. It fails with:

java.lang.IllegalArgumentException: Value contains code point U+0000
	at java.prefs/java.util.prefs.AbstractPreferences.put(AbstractPreferences.java:257)
	at org.scijava.prefs.DefaultPrefService$SmartPrefs.put(DefaultPrefService.java:393)
	at org.scijava.prefs.DefaultPrefService.put(DefaultPrefService.java:115)
	at org.scijava.module.DefaultModuleService.save(DefaultModuleService.java:306)
	at org.scijava.module.process.SaveInputsPreprocessor.saveValue(SaveInputsPreprocessor.java:77)
	at org.scijava.module.process.SaveInputsPreprocessor.process(SaveInputsPreprocessor.java:68)
	at org.scijava.module.ModuleRunner.preProcess(ModuleRunner.java:105)
	at org.scijava.module.ModuleRunner.run(ModuleRunner.java:157)
	at org.scijava.module.ModuleRunner.call(ModuleRunner.java:127)
	at org.scijava.module.ModuleRunner.call(ModuleRunner.java:66)
	at org.scijava.thread.DefaultThreadService$3.call(DefaultThreadService.java:238)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:844)