## What changes were proposed in this pull request?

When JVM backend fails without going proper error handling (eg. process crashed), the R error message could be ambiguous.

```
Error in if (returnStatus != 0) { : argument is of length zero
```

This change attempts to make it more clear (however, one would still need to investigate why JVM fails)

## How was this patch tested?

manually

Author: felixcheung <felixcheung_m@hotmail.com>

Closes #12622 from felixcheung/rreturnstatus.