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Enabling React Native Debug mode causes Error: Must first create RPC session with a valid host from rpc.js:314

See original GitHub issue

Goals

Enable React Native Debug mode in order to troubleshoot console errors, set breakpoints, profile app, and monitor network requests.

Expected Results

Mobile app connects to React Native Debugger successfully and I’m able to set breakpoints, profile app, and monitor network requests, view console errors

Actual Results

Mobile App crashes with the following error

Error: Must first create RPC session with a valid host from rpc.js:314

:19

Mobile App

Sentry Stacktrace

Error: Must first create RPC session with a valid host
  File "app:///rpc.js", col 18, in sendRequest
  File "app:///rpc.js", col 41, in setTimeout$argument_0
  File "app:///JSTimers.js", col 17, in _allocateCallback$argument_0
  File "app:///JSTimers.js", col 6, in _callTimer
  File "app:///JSTimers.js", col 6, in callTimers
  at <unknown>(app:///RNDebuggerWorker.js:2:134503)

React Native Debugger console

Steps to Reproduce

Run yarn android to build react native application and install on device
Shake device to reveal developer menu and select Debug . This is successful if the user is not logged in

Login to account which causes realm database to be initialized
An exception occurs on mobile app

![https://user-images.githubusercontent.com/222459/96701643-bea69400-1388-11eb-911e-9ee8323b2795.png](https://user-images.githubusercontent.com/222459/96701643-bea69400-1388-11eb-911e-9ee8323b2795.png)

The crash occurs when the following is called **`Realm.schemaVersion(Realm.defaultPath)`**     **`Realm.defaultPath`** displays an error when inspected using React Native debugger. See video below```


## Code Sample
<!---
Please provide a code sample or test case that highlights the issue.
If relevant, include your model definitions.
For larger code samples, links to external gists/repositories are preferred.
Full projects that we can compile and run ourselves are ideal!
-->

```jsx
export const runMigration = ({currentSchema}: {currentSchema: any}) => {
  if (!schemas.length) {
    return {schemaVersion: 0};
  }

  **let nextSchemaIndex = Realm.schemaVersion(Realm.defaultPath);**
  schemas[schemas.length - 1].schema = currentSchema;

  // If -1, it means this is a new Realm file, so no migration is needed
  if (nextSchemaIndex !== -1) {
    while (nextSchemaIndex < schemas.length) {
      const migratedRealm = new Realm(schemas[nextSchemaIndex++]);
      migratedRealm.close();
    }
  }

  return {schemaVersion: schemas[schemas.length - 1].schemaVersion};
};