When javadoc is specified with --release 8 and -subpackages causes the following (redacted) crash within javac.

java.lang.AssertionError
at jdk.compiler/com.sun.tools.javac.util.Assert.error(Assert.java:155)
at jdk.compiler/com.sun.tools.javac.util.Assert.checkNonNull(Assert.java:62)
at jdk.compiler/com.sun.tools.javac.comp.Modules.allModules(Modules.java:1127)
at jdk.javadoc/jdk.javadoc.internal.tool.ElementsTable.findModuleOfPackageName(ElementsTable.java:768)
at jdk.javadoc/jdk.javadoc.internal.tool.ElementsTable.computeSubpackages(ElementsTable.java:467)
at jdk.javadoc/jdk.javadoc.internal.tool.ElementsTable.computeSpecifiedPackages(ElementsTable.java:652)
at jdk.javadoc/jdk.javadoc.internal.tool.ElementsTable.analyze(ElementsTable.java:329)
at jdk.javadoc/jdk.javadoc.internal.tool.JavadocTool.getEnvironment(JavadocTool.java:205)
at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:591)
at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:424)
at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:341)
at jdk.javadoc/jdk.javadoc.internal.tool.Main.execute(Main.java:63)
at jdk.javadoc/jdk.javadoc.internal.tool.Main.main(Main.java:52)
2 errors
9 warnings