Fill holes explicitly (default value of newArray may not match hole value).

Author: iamstolis

graal-js/src/com.oracle.truffle.js/src/com/oracle/truffle/js/runtime/array/dyn/AbstractWritableArray.java

@@ -703,6 +703,7 @@ private ScriptArray addRangeGrow(JSDynamicObject object, Object array, int array
             arraySetArray(object, newArray);
             arraySetUsedLength(object, usedLength + size);
             if (isHolesType()) {
+                fillWithHoles(newArray, offset, offset + size);
                 arraySetHoleCount(object, arrayGetHoleCount(object) + size);
             }
             return this;