Thanks @larowlan for quick feedback.
Fixed the issues related to strict check...

Thanks @larowlan for quick feedback.

Fixed the issues related to strict checking.

About replacing '_none' or '' with class constant - I would request to keep it in #2448545: Convert '_none' option to a constant and deprecate form_select_options() only as it will be out of scope for current ticket + changes required for #2448545 are even outside the Options core module. There are many references to '_none' outside the module so it makes more sense to create the constant in core itself (outside the module). Approach and solution in #2448545 look good to me (and for sure it is going through it's own review cycle), only issue I see is bit of rework required in one of the patches after the other patch is merged, which should be fine IMO.