#3879 NPE occurs in TokenMaker

[Meg]

jEdit version: 5.1.0
platform: CentOs 5.10
Java version: 1.6.0_45
steps to reproduce:

public void test450() throws Throwable {
org.gjt.sp.jedit.buffer.JEditBuffer var0 = new org.gjt.sp.jedit.buffer.JEditBuffer();
org.gjt.sp.jedit.syntax.TokenMarker var4 = var0.getTokenMarker();
org.gjt.sp.jedit.syntax.TokenMarker.LineContext var6 = new org.gjt.sp.jedit.syntax.TokenMarker.LineContext();
org.gjt.sp.jedit.syntax.DefaultTokenHandler var8 = new org.gjt.sp.jedit.syntax.DefaultTokenHandler();
org.gjt.sp.util.SegmentBuffer var10 = new org.gjt.sp.util.SegmentBuffer(32768);
org.gjt.sp.jedit.syntax.TokenMarker.LineContext var12 = var4.markTokens(var6, (org.gjt.sp.jedit.syntax.TokenHandler)var8, (javax.swing.text.Segment)var10);
}

Expected result: No NPE
StackTrace:
88) test450(RandoopTest0)java.lang.NullPointerException
at org.gjt.sp.jedit.syntax.TokenMarker.markTokens(TokenMarker.java:120)
at RandoopTest0.test450(RandoopTest0.java:8709)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

[Meg]

public synchronized LineContext markTokens(LineContext prevContext,
    TokenHandler tokenHandler, Segment line)
{
    ...

    context = new LineContext();

    if(prevContext == null)
    {
        context.rules = getMainRuleSet();
        context.escapeRule = context.rules.getEscapeRule();
    }
    else
    {
        context.parent = prevContext.parent;
        context.setInRule(prevContext.inRule);
        context.rules = prevContext.rules;
        context.spanEndSubst = prevContext.spanEndSubst;
        context.spanEndSubstRegex = prevContext.spanEndSubstRegex;
    }

    keywords = context.rules.getKeywords(); --> NPE
    ...
}

context.rules is assigned in both branches before the refrence. Although context.rule can be null, there is no proper error handling before use.

[Dale Anson]

Your test is missing setting the rules in the previous context, var6.