The following items are included in this issue:
1) The setDependentDropdownValuesJs.ftl is using an incorrect argument which usually happens to work because it is a duplicate of another. See patch for details
2) The getDependentDropdownValues.js is modified with a new argument to allow for empty selections. Therefore, copying the behavior of form widget drop-down's "allow-empty"
3) There is only one file affected by item number 2 above, therefore, I fixed it to include the argument in getDependentDropdownValues.js