Function nullable

nullable<T>(val: T, map: (val: T) => Dict<T>): false | Dict<T>
Function to be used to construct an update object. If value is undefined - property will not be updated. If value is null - it will be set. Useful for Date properties. Example:
```
   await update('table_name',
     {
       title: element.title,
       ...nullable(element.released, val => ({ released: val })),
     },
     { id: elementId },
   ).run(ctx);
```
Type Parameters
- T
Parameters
- val: T
  value to be used to update a property
- map: (val: T) => Dict<T>
  mapping function that will return an update object for the property
Returns false | Dict<T>