Fix modular autoinit breakage

I ran into this issue updating dependencies for a Nuxt 3 app. The problem is that `process.{client,server,dev}` are defined even on the client, so the client ends up broken with errors like:

```
Uncaught TypeError: can't access property "__FIREBASE_DEFAULTS__", process.env is undefined
```

Since the code only uses `process.env`, this updates the check to look explicitly for `process.env`.

Author: bcspragu

packages/util/src/defaults.ts

@@ -57,7 +57,7 @@ const getDefaultsFromGlobal = (): FirebaseDefaults | undefined =>
  * process.env.__FIREBASE_DEFAULTS_PATH__
  */
 const getDefaultsFromEnvVariable = (): FirebaseDefaults | undefined => {
-  if (typeof process === 'undefined') {
+  if (typeof process == 'undefined' || typeof process.env === 'undefined') {
     return;
   }
   const defaultsJsonString = process.env.__FIREBASE_DEFAULTS__;