test failed with unexpected ArrayIndexOutOfBoundsException

A DESCRIPTION OF THE PROBLEM :
We generate a unit test automatically, and the test failed. The test case is as below:


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
 @Test
  public void test_setTo(){
      long long1 = 1L;
      long long2 = 0L;
      jdk.nashorn.internal.runtime.BitVector bitVector0 = new jdk.nashorn.internal.runtime.BitVector(long2);
      bitVector0.setTo(long1);
  }

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
do not throw ArrayIndexOutOfBoundsException
ACTUAL -
java.lang.ArrayIndexOutOfBoundsException: 0

at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.BitVector.setTo(BitVector.java:169)


---------- BEGIN SOURCE ----------
/**
     * Sets all bits in the vector up to the length.
     *
     * @param length max bit where to stop setting bits
     */
public void setTo(final long length) {
        if (0 < length) {
            final int lastWord = (int)(length >> BITSHIFT);
            final long lastBits = (1L << (int)(length & BITMASK)) - 1L;
            Arrays.fill(bits, 0, lastWord, ~0L);

            if (lastBits != 0L) {
                bits[lastWord] |= lastBits;
            }
        }
    }
---------- END SOURCE ----------

FREQUENCY : occasionally