FIREBASE_DATABASE_EMULATOR_HOST environment variable with IP address errors and exits application

### [REQUIRED] Step 2: Describe your environment

* Operating System version: Windows 11 Pro
* Firebase SDK version: firebase.google.com/go/v4
* Library version: _____
* Firebase Product: database

### [REQUIRED] Step 3: Describe the problem

Setting the FIREBASE_DATABASE_EMULATOR_HOST environment variable with an IP address errors and exit's the application.

#### Steps to reproduce:

Create an application using the firebase sdk for golang
Load FIREBASE_DATABASE_EMULATOR_HOST={IP_ADDRESS} into your environment
The application should crash

#### Relevant Code:

```go
package firebase

import (
"context"
"log"
"os"

fb "firebase.google.com/go/v4"
"google.golang.org/api/option"
)

func Firebase(ctx context.Context) *fb.App {
db := os.Getenv("DATABASE_URL")
if db == "" {
log.Fatal("Error loading DATABASE_URL from .env file")
}
pid := os.Getenv("PROJECT_ID")
if pid == "" {
log.Fatal("Error loading PROJECT_ID from .env file")
}
config := &fb.Config{
DatabaseURL: db,
ProjectID: pid,
}
env := os.Getenv("APP_ENV")
var opt option.ClientOption
if env == "development" {
cred := os.Getenv("FIREBASE_CONFIG")
if cred == "" {
log.Fatal("Error loading FIREBASE_CONFIG from .env file")
}
opt = option.WithCredentialsFile(cred)
}
if value := os.Getenv("FIRESTORE_EMULATOR_HOST"); value != "" {
log.Printf("Using Firestore Emulator: %s", value)
app, err := fb.NewApp(ctx, config, opt)
if err != nil {
log.Fatalln(err)
}
return app
} else {
app, err := fb.NewApp(ctx, config)
if err != nil {
log.Fatalln(err)
}
return app
}
}
```