has_trait_rank trigger should not require rank field

[TungstnBallon]

Currently this code:

has_trait_rank = {
    trait = beauty_good
    character > primary_heir
}

returns these 2 errors:

• Missing rank, expecting at least 1 CW242(CW242)
• character is unexpected in has_trait_rank CW262(CW262)

However the game allows this (copy pasted from the wiki):

has_trait_rank = {
    trait = TRAIT_GROUP
    rank <=> number (can be script value) # need only one of rank or character
    character <=> character target # need only one of rank or character
}