ID 394403 - Modo crashes when adding clip type values to a Form Command List.

Problem summary
Modo crashes when adding clip type values to a Form Command List.

Customer reported version
modo.13.0v1

Customer reported platform
windows10

Steps to reproduce
1) Open Modo.
2) Select Layout > Layouts > Scripting
3) Copy the Form Command List example from the SDK documentation: http://sdk.luxology.com/wiki/Form_Command_List_example
4) Paste the command into the script editor in Modo, then modify

cmdlist = ['item.name',
           # A string in the list that starts with a dash (hyphen) followed by 
           # a space becomes a line divider in the form.
           '- ',
           'item.color',
           'item.comment',
           # A string in the list that starts with a dash (hyphen) followed by 
           # a space and then a string becomes a labelled divider in the form.
           '- I am a Divider',
           'item.create',
           'item.tagAdd']

to:

cmdlist = ['item.name',
           # A string in the list that starts with a dash (hyphen) followed by 
           # a space becomes a line divider in the form.
           '- ',
           'item.color',
           'item.comment',
           # A string in the list that starts with a dash (hyphen) followed by 
           # a space and then a string becomes a labelled divider in the form.
           '- I am a Divider',
           'item.create',
           'item.tagAdd',
           'user.value my.command1 ?']

5) Press "Ctrl + Enter" to run the script.
6) In the command bar at the bottom, enter and run the following command:
user.defNew my.command1 &clip temporary
7) Select System > Form Editor
8) Select "Create" then click "New Form."
9) Enter "FCLCrash" for the Form Name and click "OK."
10) Click "(new control)," then "Add Command." In the resulting window, add the following command and click OK:
replace.me ?
11) Select "Preview Form" in the top right.
Result: Modo will crash.

Expected behaviour
Modo should not crash when adding a clip to a form command list.

Actual behaviour
Modo crashes when adding a clip to a form command list

Workaround
Unknown.

Reproduced by support
This bug has been reproduced in:
13.0v1 - Windows 10, OSX 10.13.5
12.2v2 - Windows 10
12.2v1 - Windows 10, OSX 10.13.5 

Unable to reproduce bug in:
12.1v2 - Windows 10, OSX 10.13.5

Earliest version tested
12.1v2 - Windows 10, OSX 10.13.5 - This issue no longer appears in this version and has regressed