[BugFix] Safely Access openapi_extra When None

[deeleeramone]

1. Why?:

   • There were a couple of spots where openapi_extra was being accessed as a dictionary when the value was None.

2. What?:

   • Fixes those instances to include the None check.

3. Impact:

   • Custom extensions, Platform endpoints will have items in the openapi_extra slot.

4. Testing Done:

   • Custom Router extension, create the function by directly accessing APIRouter instance.

@router._api_router.get("/get_data_choices")