Empty EnumSet can't be used after being deserialized

[francisu]

Adding these lines to the end of TestSet.testSet() shows the problem.

  ```

testSet._enumSet.remove(ManySets.EnumValues.E1);
testSet._enumSet.remove(ManySets.EnumValues.E2);
testSet._enumSet.remove(ManySets.EnumValues.E3);
json = TestUtil.getJsonString(testSet)
testSet = (ManySets) TestUtil.readJsonObject(json)
testSet._enumSet.add(ManySets.EnumValues.E1);

The problem is the elementType is null when the EnumSet is deserialized, and then it cannot be used to add values. The elementType needs to be retained during the serialization/deserialization process and it's not.

[jdereg]

Looking into this.

[laurgarn]

I think below merge-request fixes this (too)
#180

[jdereg]

Fixed in 4.14.1