Undefined unavailableDate crash in DateRangePicker when using SSR optimized localized strings

### Provide a general summary of the issue here

When using latest `@react-aria/optimize-locales-plugin` in next.js for optimizing locales with `react-aria-components` package the datepicker crashes the page.

The error call stack looks like this:
```
TypeError: Cannot read properties of undefined (reading 'unavailableDate')
at a.getStringForLocale (LocalizedStringDictionary.mjs:17:1)
at o.format (LocalizedStringFormatter.mjs:15:1)
at y (utils.mjs:51:1)
at useDatePickerState.mjs:58:98
at Object.aQ [as useMemo] (react-dom.production.min.js:179:117)
at n.useMemo (react.production.min.js:25:191)
at L (useDatePickerState.mjs:58:47)
at useDatePickerState.mjs:121:1
at ab (react-dom.production.min.js:167:135)
at uo (react-dom.production.min.js:193:55)
```

### 🤔 Expected Behavior?

The `@react-aria/optimize-locales-plugin` package should let me optimize which locales I want to include in my bundle without crashing pages using the datepicker.

### 😯 Current Behavior

- If the Datepicker isDateUnavailable callback returns true, the page will crash because of missing unavailableDate in provided locale.

### 💁 Possible Solution

A similar issue was fixed in https://github.com/adobe/react-spectrum/pull/6286. Maybe something needs to be adjusted for unavailableDate.

### 🔦 Context

_No response_

### 🖥️ Steps to Reproduce

git clone https://github.com/ihsib/react-aria-datepicker--locale-optimize-bug

npm install

npm run build

npm run start

Open [http://localhost:3000](http://localhost:3000) try inputting a date in the past with the keyboard for example 2023-01-01

### Version

1.2.1

### What browsers are you seeing the problem on?

Microsoft Edge

### If other, please specify.

_No response_

### What operating system are you using?

Windows

### 🧢 Your Company/Team

_No response_

### 🕷 Tracking Issue

_No response_