ADDITIONAL SYSTEM INFORMATION :
java openjdk 11.0.4 on windows 10 build 17763.1369

A DESCRIPTION OF THE PROBLEM :
[javac] An exception has occurred in the compiler (11.0.4). Please file a bug against the Java compiler via the Java bug reporting page (http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com) for duplicates. Include your program and the following diagnostic in your report. Thank you.
    [javac] java.lang.NullPointerException
    [javac] at jdk.compiler/com.sun.tools.javac.code.Symtab.lookupPackage(Symtab.java:666)
    [javac] at jdk.compiler/com.sun.tools.javac.code.ClassFinder.loadClass(ClassFinder.java:424)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Resolve$6.lambda$loadClass$3(Resolve.java:2027)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Resolve.lookupInvisibleSymbol(Resolve.java:2127)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Resolve$6.loadClass(Resolve.java:2020)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Resolve.loadClass(Resolve.java:2001)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Resolve.findIdentInPackageInternal(Resolve.java:2386)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Resolve.findIdentInPackage(Resolve.java:2374)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Attr.selectSym(Attr.java:3716)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Attr.visitSelect(Attr.java:3601)
    [javac] at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCFieldAccess.accept(JCTree.java:2114)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Attr.attribTree(Attr.java:655)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Attr.attribType(Attr.java:715)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.Attr.attribType(Attr.java:708)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.attribImportType(TypeEnter.java:441)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.doImport(TypeEnter.java:424)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.resolveImports(TypeEnter.java:364)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$ImportsPhase.runPhase(TypeEnter.java:321)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.doCompleteEnvs(TypeEnter.java:282)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.TypeEnter$Phase.completeEnvs(TypeEnter.java:251)
    [javac] at jdk.compiler/com.sun.tools.javac.comp.TypeEnter.complete(TypeEnter.java:198)

REGRESSION : Last worked in version 11

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Happened during a compile of a large java project.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
compiling java does not produce a null pointer exception
ACTUAL -
received a null pointer exception at the above line

CUSTOMER SUBMITTED WORKAROUND :
Changed ant build.xml so that the error no longer occurred. It shouldn't happen but it did.

FREQUENCY : rarely