How to handle null values from API in a dropdown widget?

I have a dropdown that is populated with api values. The option values are Int type and the label values String type, as I show below.

Unfortunately, when the api returns a null value, the widget breaks. I have tried to create two custom functions to validate if the JSON type (from the api) is null and if so, return [], but couldn't solve the problem.

Now, I have two questions:

1) How to handle null values on a dropdown with int a string values?

2) Is there any smart way to handle null safety using one function to all data types or I have to create nullcheck for each data type I use?

PS: I created two functions, one to return int type and another to string type.

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