[Form] Add missing default property typeExtensionServiceIds

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Just added missing property. 

It works pretty well for now as `$typeExtensionServiceIds` is setted in construct but could bring misunderstood or strange behavior in future.