IAE in Formatter option windows

[mbien]

regression since #7382

SEVERE [org.openide.util.RequestProcessor]: Error in RequestProcessor org.netbeans.modules.java.file.launcher.queries.MultiSourceRootProvider$AttributeBasedClassPathImplementation$$Lambda/0x00007fbde7e949a8
java.lang.IllegalArgumentException: URI scheme is not "file"
	at java.base/java.io.File.<init>(File.java:423)
	at org.openide.util.BaseUtilities.toFile(BaseUtilities.java:1617)
	at org.openide.util.Utilities.toFile(Utilities.java:2174)
	at org.netbeans.modules.java.file.launcher.queries.MultiSourceRootProvider$AttributeBasedClassPathImplementation.doUpdateDelegates(MultiSourceRootProvider.java:302)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1420)
	at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:45)
	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:287)
	at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2035)

repro:

1. open any window which includes Formatting options, e.g via the main options window or via project properties
2. (switch language to java if needed)
3. check log.