Fix fast flag editor showing an error when trying to add a fast flag with _PlaceFilter or _DataCenterFilter

[srthMD]

Before, trying to add a fast flag with a place filter like the one below would present an error saying the value was
invalid depending on the required type.

{
    "FFlagSoundsUsePhysicalVelocity_PlaceFilter": "true;292439477"
}

After, importing the same json now will successfully import the fast flag and the changes will apply.

And if the place filter is invalid, like a trailing semicolon, it will error

Closes #2348

(sorry if theres any issues, this is my first time making a pr)

[pizzaboxer]

Validation code looks good, actually is more than what I would've done.