FIX Use correct argument for FormBuilder context

[emteknetnz]

Issue #1778

[GuySartorelli]

I can't de-select a record from the single SearchableDropdownField in an elemental block anymore.
I can select a new record, but not deselect one that was already saved into the field.

[emteknetnz]

I think this might just a be bad default when lazy-loading

Things are "clearable" by default when not lazy-loading because there's a default blank option that's selectable. This option is not there however when you lazy-load. I can solve this by setting ->setIsClearable(true) alongside ->setIsLazyLoaded(true) then I can clear the value.

I think the solution here is that we just update the field to be clearable by default? This won't be a breaking change, just a behavioural change we could ship in 5.3

Note that clicking the little 'x' when it's clearable will clear ALL selected options for the mutli version of the field, though this seems like it's still a good default to me

I'll make a new issue for this

[emteknetnz]

New issue to ensure field is always clearable #1791

[GuySartorelli]

LGTM