Disabling Form Select Option based on value (Gravity Form)

select-option-disable.js

// This was specifically for Gravity Form i wanted to disable options based on a null value. 
// In the dropdown I had, some values were used as headers so people would know the type of 
// item they were selecting -- in this case the dropdown was for liquor/wine selection

// Before to put the "true" part after disabled rather than leaving it blank 
// or it won't work in any browser but Chrome (Mac). 

// gForm disable select options with null or '|0' value
$('.gform_body select option[value="null|0"]').attr("disabled","true");

// For Safari if the above doesn't work use this 
// gForm disable select options with null or '|0' value
$('.gform_body select option[value="null|0"]').attr("disabled","disabled").prop("disabled", true);

Where do I place it?