Build failing when using app.json splash config without backgroundColor - AAPT: error: resource color/splashscreen_background

### Summary

Android build using on local and remote EAS build if app.json splash:{ backgroundColor } is not specified.

I upgraded the app from expo 49 to expo 51 and the eas-cli to lastest version. Previously the app build worked without issues for android with only splash:{ image } being specified. After the upgrade the build fails and the solution was to add a color value for the splash:{ backgroundColor } attribute

fails:
```json
{
"expo": {
"splash": {
"image": "./app/assets/splashscreen_background.png"
}
}
}
```

succedes:
```json
{
"expo": {
"splash": {
"image": "./app/assets/splashscreen_background.png",
"backgroundColor": "#ffffff"
}
}
}
```

### Managed or bare?

Managed

### Environment

```
| expo-env-info 1.2.0 environment info:
System:
OS: macOS 13.6.7
Shell: 5.9 - /bin/zsh
Binaries:
Node: 18.20.2 - ~/.asdf/installs/nodejs/18.20.2/bin/node
Yarn: 3.2.1 - ~/.asdf/installs/nodejs/18.20.2/bin/yarn
npm: 10.5.0 - ~/.asdf/plugins/nodejs/shims/npm
Watchman: HEAD-067252e - /opt/homebrew/bin/watchman
SDKs:
iOS SDK:
Platforms: DriverKit 22.2, iOS 16.2, macOS 13.1, tvOS 16.1, watchOS 9.1
IDEs:
Android Studio: 2022.2 AI-222.4459.24.2221.10121639
Xcode: 14.2/14C18 - /usr/bin/xcodebuild
npmPackages:
expo: 51 => 51.0.14
react: 18.2.0 => 18.2.0
react-native: 0.74.2 => 0.74.2
npmGlobalPackages:
eas-cli: 10.0.2
Expo Workflow: managed
```

```
✔ Check Expo config for common issues
✔ Check package.json for common issues
✔ Check native tooling versions
✔ Check dependencies for packages that should not be installed directly
✔ Check for common project setup issues
✔ Check for issues with metro config
✔ Check npm/ yarn versions
✔ Check Expo config (app.json/ app.config.js) schema
✔ Check that packages match versions required by installed Expo SDK
✔ Check that native modules do not use incompatible support packages
✔ Check for legacy global CLI installed locally
✔ Check that native modules use compatible support package versions for installed Expo SDK

Didn't find any issues with the project
```

### Error output
```
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:processReleaseResources'.
> A failure occurred while executing com.android.build.gradle.internal.res.LinkApplicationAndroidResourcesTask$TaskAction
> Android resource linking failed
ERROR: /home/expo/workingdir/build/android/app/src/main/res/drawable/splashscreen.xml:2: AAPT: error: resource color/splashscreen_background (aka com.app.redactred:color/splashscreen_background) not found.

* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
> Get more help at https://help.gradle.org.
BUILD FAILED in 8m 15s
```
### Reproducible demo or steps to reproduce from a blank project

I don't have time to create demo but I assume if you create project with the latest expo
add `app.json`/`app.config.js` splash with `image` without `backgroundColor` property and use `eas` to build the app for android.

Current behaviour is not consistent with the expo-doctor schema validation, and with types specified for ExpoConfig where the backgroundColor is optional.