Crash for overlap between source path and patch module path

ADDITIONAL SYSTEM INFORMATION :
Microsoft Windows [Version 10.0.17763.292]
JDK 11.0.2
JDK 12-ea+29
JDK 13-ea+5

A DESCRIPTION OF THE PROBLEM :
1. Run testcase
2. javadoc tool crashes with:

javadoc: error - fatal error encountered: java.lang.NullPointerException
javadoc: error - Please file a bug against the javadoc tool via the Java bug reporting page
(http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com)
for duplicates. Include error messages and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
        at java.base/java.util.Objects.requireNonNull(Objects.java:221)
        at jdk.compiler/com.sun.tools.javac.file.BaseFileManager.nullCheck(BaseFileManager.java:497)
        at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.contains(JavacFileManager.java:955)
        at jdk.compiler/com.sun.tools.javac.comp.Modules.checkSourceLocation(Modules.java:539)
        at jdk.compiler/com.sun.tools.javac.comp.Modules.setCompilationUnitModules(Modules.java:529)
        at jdk.compiler/com.sun.tools.javac.comp.Modules.enter(Modules.java:267)
        at jdk.compiler/com.sun.tools.javac.comp.Modules.enter(Modules.java:248)
        at jdk.javadoc/jdk.javadoc.internal.tool.JavadocTool.getEnvironment(JavadocTool.java:201)
        at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:576)
        at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:432)
        at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:345)
        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


FREQUENCY : always