[Bug] Error in JavaScript Resolver with default initialization using the 'let' keyword

In an AppSync JavaScript resolver there is a strange bug where if I use the `let` keyword to define a default value and then conditonally change it, deployment fails (with a `BadRequestException`):

```js
export function request(ctx) {
const { productCode } = ctx.args;

// We can look at the fields selected in the query and scope our DynamoDB query narrower if items are not requested
const { selectionSetList } = ctx.info;

// Default to the wider query (using ge) including items
let SK = { ge: `#PRODUCT#${productCode}` };

// And only narrow (using eq) to exclude items if the selectionSetList explicitly doesn't include itemSummaries
if (selectionSetList != null && !selectionSetList.includes('items')) {
SK = { eq: `#PRODUCT#${productCode}` };
}

// ...
}
```

Whereas if I use an `if...else` and avoid default initialization, it succeeds:

```js
export function request(ctx) {
const { productCode } = ctx.args;

// We can look at the fields selected in the query and scope our DynamoDB query narrower if items are not requested
const { selectionSetList } = ctx.info;

let SK;

// Only narrow (using eq) to exclude items if the selectionSetList explicitly doesn't include itemSummaries
if (selectionSetList != null && !selectionSetList.includes('items')) {
SK = { eq: `#PRODUCT#${productCode}` };
} else {
// Otherwise default to the wider query (using ge) including items
SK = { ge: `#PRODUCT#${productCode}` };
}

// ...
}
```

The issue provides two AppSync JavaScript resolver variants but names no repository files or tests. Reproduce both snippets as AppSync resolvers and compare deployment results; done means identifying and documenting or correcting the behavior so the intended conditional DynamoDB query deploys successfully.

Written by the indexing model from the issue text.