Please see the minimized test below to reproduce the issue.

Minimized test:
===============
$ cat test.java
import java.lang.invoke.*;
import java.util.Arrays;

public class test {
    public static void main(String[] args) throws Throwable {
        MethodHandle dts = MethodHandles.publicLookup().findStatic(
                Arrays.class,
                "deepToString",
                MethodType.methodType(String.class, Object[].class));
        dts.asCollector((Class) null, 1);
    }
}

Minimized test output:
======================
$ java -version
java version "1.7.0-ea"
Java(TM) SE Runtime Environment (build 1.7.0-ea-b142)
Java HotSpot(TM) Server VM (build 21.0-b12, mixed mode)

$ java -verify test
Exception in thread "main" java.lang.NullPointerException
        at java.lang.invoke.MethodHandle.asCollector(MethodHandle.java:783)
        at test.main(test.java:10)

If the behaviour just need to be documented in javadoc then please feel free to close this CR as duplicate of 7032323.