Export fails in v3.8.1

```
export "Internal/project" {
    formats tjp
    definitions tasks
    taskattributes complete, flags, note, booking
    resourceattributes -
}

```
results in:
```
./reports.tji:347: Error: Cannot write to file Internal/project.tji.
No such file or directory @ rb_sysopen - Internal/project.tji
```