Just downloaded v2.30.0 for the virtual property compound assignment, and it's mostly great but there does seem to be an issue. Here's a snippet of the registration:

ASengine->RegisterObjectType("jjOBJ", sizeof(Omonster), asOBJ_REF | asOBJ_NOCOUNT );
ASengine->RegisterObjectMethod("jjOBJ", "uint16 get_creatorID() const", asFUNCTION(getCreatorID), asCALL_CDECL_OBJFIRST);
ASengine->RegisterObjectMethod("jjOBJ", "uint16 set_creatorID(uint16)", asFUNCTION(setCreatorID), asCALL_CDECL_OBJFIRST);
ASengine->RegisterGlobalFunction("jjOBJ @get_jjObjects(int)", asFUNCTION(getObject), asCALL_CDECL);

Given that, any of these run fine:

    jjObjects[0].creatorID = jjObjects[0].creatorID + 2;
//or
    jjOBJ@ obj = jjObjects[0];
    obj.creatorID = obj.creatorID + 2;
//or
    jjOBJ@ obj = jjObjects[0];
    obj.creatorID += 2;

But either of these versions produce a Null Pointer Access exception:

    jjObjects[0].creatorID += 2;
//or
    get_jjObjects(0).creatorID += 2;

The problem seems to exist for any function that returns a handle, even ones that aren't registered as get_*; that was just the easiest one to test given my existing registration. If creatorID is registered with RegisterObjectProperty instead, nothing goes wrong.