I'm creating a simple block for making times ("4:00pm") that can also have a "now" option. To accomplish this, I'm using the mutation settings. However, my Blockly must be a little rusty because I can't figure out what's wrong with it. I've modeled the code after the builtin "math_number_property" block, except I'm dynamically creating drop-downs instead of value inputs.
http://pastebin.com/raw/LW12cRQr
With the code above, it works fine until you try and change the current time from "now" to anything else, in which case it triggers the following error.

Any ideas? Am I doing something wrong with how I dynamically instantiate the dropdowns?
Thanks,
~Cory